Literary theory and criticism is a specialized field of study. If you're talking to people who haven't studied it or who have just a passing acquaintance with it, you may encounter some generalizations about what it is and its value. Here are a few of the most common misunderstandings about literary theory.
That it is something new.
One of the most common misconceptions that you may encounter is that literary theory is something "new" or "trendy." Wrong - the history of literary theory stretches back all the way to the ancient Greeks. Over its long history, literary criticism has taken on many forms, from philosophizing about literary works to book reviewing to becoming a part of the modern system of academic disciplines. The forms it takes change from one era to the next, but it's a mistake to ignore the long history of theory before the modern era
That it is something old.
That said, you do need to historicize literary theory and not make the mistake of thinking that Plato's ideas grow out of the same context as Judith Butler's. Institutional, social, political, and historical contexts all matter.
That it distorts literature.
This is a frequent complaint -- that reading literary theory and criticism "misreads" texts, that readers need to just read "straight" in order to understand what the author meant. The study of literary theory helps you to see that this is a misconception -- there is no "right" way to read a text. As Stanley Fish says in his influential essay "Interpreting the Variorum," "The choice is never between objectivity and interpretation but between an interpretation that is unacknowledged and an interpretation that is at least aware of itself." In other words, the act of reading is inherently an act of interpretation. The more you're aware of your own preferences and expectations as a reader, the better off you will be. The more widely you read, the more you'll be open to multiple genres, styles of writing, and modes of interpretation.
That it ruins the reading experience.
Going along with the idea that theory "distorts" literature is the sense that it "ruins" reading. Anyone whose experience of a text can be ruined by knowing more about different critical approaches is either too caught up in their own subjective preferences or not a very comfortable reader to begin with. Knowing that someone else interpreted a text differently than you should inspire you to think through and defend your interpretation, not to throw up your hands in despair.
If you're reading a piece of literature for the first time, avoid criticism until you've experienced the text for yourself. This includes editorial introductions to a work. Oftentimes critics are so immersed in the text that they forget others are experiencing it for the first time, so they will "spoil" plot developments in critical articles or even book introductions. I once taught an edition of a Gothic novel where a plot twist that only occurs in the last chapter of the novel was "spoiled" on the back of the book jacket!
That it is difficult.
Theory has a reputation for being difficult, incomprehensible, pseudo-scientific, and jargony. To some extent this is a misconception. Every academic discipline has its own technical vocabulary, and literary studies is no different. Literary critics use a specialized language to talk about things for which there isn't everyday language, giving names to particular figures of speech, poetic forms, metrical patterns, psychological phenomena, social structures, and all kinds of other things. But there's also a wealth of literary criticism that is extremely accessible, particularly some of the older works of criticism.
That it is easy.
If literary theory and criticism were completely easy, it wouldn't be an academic subject at all. Theory requires you to think in careful and rigorous ways, in a manner similar to philosophical investigation. Theorists need to define their terms carefully and judiciously. You might encounter some academic studies of literature where the author just seems to be showing off how many multisyllabic words and subordinate clauses they can fit into a single sentence. Skip over those types of academic articles (which became quite common at the height of the theory revolution in the 1980s and 1990s) unless absolutely necessary. Don't dive right into the pages of a specialized academic journal; work your way up to it by studying a bit more about the history of theory, learning some terms, and learning some strategies for reading literary theory first.
That it can neatly be divided into "camps."
Theoretical methodologies and critical approaches can often be labeled. But labeling a theoretical approach isn't like joining a cult or pledging a fraternity. Particularly at this moment in literary studies, most people don't choose to label themselves as one particular type of critic. Instead, scholars see the range of critical approaches and terms as a toolbox from which they can select the most appropriate tool for a particular task. You might be a feminist scholar while studying early women writers, a historicist when looking at the poets of World War I, and a narratologist while reading a particularly convoluted short story. Or you might pick and choose from a variety of approaches within a single essay.
Some theoretical approaches might seem incompatible with each other - an emphasis on form alone seems to be at odds with an emphasis on politics, for example. But in most cases the incompatibility vanishes the closer you look.
That it's all about "deconstructing" things.
In the 1980s and 1990s, literary theory became synonymous with "deconstruction" in the minds of some people. Often they didn't have a very good idea of what deconstruction actually is - a certain type of literary approach, one among many, that gained popularity during this time but that coexisted with a range of other approaches. Deconstruction has to do with analyzing contradictions within texts, unraveling the foundations upon which they are built, celebrating the "play" of language within literature, and a range of other things. It doesn't mean blowing things up or demolishing things, despite what its name may suggest.
So if you encounter accusations that literary critics "deconstruct" works of literature in a negative and destructive sense, one rebuttal is to ask your accuser to think of this type of approach as analogous to what an anatomist or an engineer does. Literary theorists can take apart works to see how they're made, what the building blocks are, and what presuppositions they're founded upon. It's only one of many things that theorists do, but it's an important one.
That it's "liberal."
There's a certain truth to the fact that students and professors of literature tend to be more politically liberal than other groups (say, business students). But that generalization is true across a whole range of disciplines and subjects: university professors tend to be more liberal as a group, as do humanities and fine arts students. But literary theory and criticism isn't inherently liberal, nor should it marginalize or exclude conservative voices. Many of the leading figures in the long tradition of conservative thought were also literary theorists, including Plato and Edmund Burke. Burke is a great example -- he has been called "the father of conservatism" and "the first conservative." He's also one of the most important literary theorists of the Enlightenment, helping to promulgate the concept of the sublime that inspired the Romantic movement in literature.
That it is something you choose.
Even if your theory of literature boils down to "it sucks," that's a theory and you're a critic. (I hope that's not your theory, though!) From the first moment children begin consuming bedtime stories, their ideas about storytelling, literature, and interpretation are forming -- they want to see the princess have a happy ending or secretly root for the wicked witch, they prefer certain types of stories to others, and so forth. As kids get older, they get exposed to longer and more complicated forms of storytelling and become more sophisticated readers. Their theories of literature begin to change as well.
You could think of an everyday reader as an "amateur" critic and a professor of literary studies as a "professional." But the difference here between an amateur and professional isn't the same as it is in professions that require licensure, like an "amateur" versus a "professional" doctor (stay away from those "amateur" doctors!). Perhaps sports provides a better analogy. Professional athletes are playing the same game as amateurs when it comes to tennis, golf, basketball, or what have you. The professionals just have more experience, more skills at their disposal, and get paid to play the game. Or cooking: the difference between a professional chef and your average everyday home cook has to do more with the sophistication of their technique (and the fact that they do it for a living) than with any real difference in approach. So every reader is already an amateur literary critic, whether or not they've ever thought of themselves as such. For those who aspire to more, there's an infinite world of literature and criticism waiting for you.