When I was growing up in a small town in Alabama in the 1950s, the only word ever used for something that might be called same-sex attraction or homosexuality was "queer." Of course, it always carried a very negative and hateful connotation. I can still remember cringing at the thought that it was probably I whom they were talking about. Just as other people have come to embrace negative slang like "dyke" and "faggot" to throw the words back, I have learned to embrace "queer." That definitely takes the sting out of those memories.
However, unlike the other slang terms, "queer" has come to be used by many people in a way that serves a useful purpose of inclusiveness. There are people who want to take any word that has ever been used in a nasty manner and declare it unfit for all polite discourse and conversation. One particularly problematic example of that is the notion, which I have encountered on several occasions, that because the religious right is fond of referring to "the homosexual agenda," then the word "homosexual" should never be used for any purpose. They don't seem to think that "agenda" and the definite article should go by the wayside. "Homosexual" is a word that has good and appropriate usages in medical and scientific contexts.
The media have adopted "gay" as a generic term that is loosely applied to a wide range of people with nontraditional sexual or gender identities. This is as objectionable as the traditional practice of making masculine pronouns the default for English usage. Both of these practices are not going to disappear anytime soon, but that doesn't mean that I have to follow them.
The acronym "LGBT" has come into usage as something of a stopgap measure. Most people use it to stand for "lesbian, gay, bisexual, transgender." There have been various discussions about people who are attracted by and attached to this movement that are not included under those four terms. That has resulted in the acronym being extended to "LGBTQQIA." The last four letters are for "queer, questioning, intersex, ally." Although I agree with the sprit of inclusiveness, the acronym becomes completely unweildly. Any acronym is like hitting a speed bump when you are trying to write coherent prose.
"Queer" is more than some kind of catch-all basket. When I am able to put aside my childhood memories, it really does capture a lot of how I have always felt about myself. There were a lot of things about the world in which I grew up that did not sit well with me. Well beyond my sexual identity, I have always been a person who did not easily fit in with the tribe. "Queer," in the sense of being different and unusual, captures the way I feel about myself. I reached a point in young adulthood where I finally began to enjoy that state of affairs. That was a very necessary step in my coming-out process, realizing that my personal validity does not depend on what the masses think of me.
Homo sapiens are by nature tribal animals. People who are in a minority are always going to be treated as outsiders, to some extent. Marriage equality is necessary for justice, but it will not, by itself, bring guranteed respectability. We are always going to be considered a bit queer.