I was taught early on to be a critical thinker. In my family, without that (and a strong wit) you couldn't keep up with your parents and six siblings. You had to think through all sides of what you were discussing and never be caught using pedestrian slogans you had heard at school or from friends. With so many other sharp people always in the conversation, if you took sides, you had to know why and how to defend your position.
Another thing that I learned from my family is that you should never be intentionally cruel to anyone. Primarily as a young kid, the rule applied mostly to making fun of people's personal appearance and race, which, though tied to personal appearance, was societally a much bigger issue. You did not disrespect people's appearance or race. It was cruel and wrong.
As much as critical thinking was valued, though, I still don't think it trumped the no-cruelty rule. There was no obvious underlying theory, nor deep analysis behind. It was simply a threshold position, mandatory if you were to be a decent person.
We were taught explicitly to not be racist -- which, as understood in the '60s and '70s, meant eschewing the n-word and being nice to the occasional black people we interacted with. Even though we lived in a very segregated white neighborhood in a largely segregated northern city and were exposed to overt racism constantly, we were taught with deep conviction that everyone was equal and deserved our respect. I wasn't that analytical about it; it just made sense. Black people (that's who my family and my city were talking about then) would feel bad if you disrespected them. That would be cruelty. We didn't talk about the derivation of certain words or whether they should be reclaimed from the oppressors. Some words weren't nice, and they hurt people.
Most people in America now know how it hurts for a white person to use the n-word. But now we have lots of words that some group or another has told us we shouldn't use: "lame," "illegal" "immigrant," "retarded," "faggot," "dyke," "tranny." Some people complain that we have too many such words and that it's "political correctness run amok." Some people use these proscribed words as merit badges, emblematic of independence or rebellion.
To be honest, I don't come to this debate very critically. I bring only the don't-be-cruel rule.
Certainly, many people, in every marginalized community, use these words and have every right to do so, but many others are really hurt by them. When you use these words -- whether you are a member of the community or not -- some people are hurt. Some people will see you as being cruel regardless of whether you think you have a good theoretical or political reason for doing so.
We know that "tranny" is often used to degrade trans people and is frequently spit out as hate during anti-trans violence. And we know that continuing stereotypes of trans people as "not real" women or men do real damage to society and to real people. Most importantly, though, when you use it and other words like this, some people will feel intense hurt, fairly to you or not.
It can be understandably hard for people who are not within a particular community to understand which words are OK and in which contexts. Language changes faster than ever now, especially in marginalized communities that are just developing politically. Not everyone can be expected to keep up. And it is certainly true that the offended community's reaction to celebrities using these words can seem out of proportion to the offense. For instance, I know and regret that the U.S. trans community, of which I am a part, can absolutely be inappropriately aggressive and unforgiving. But I hope that these difficulties show you how important it is to trans people and others that you try.
Words like "tranny," "faggot," "dyke," "illegal," "retard," and "lame" are often used to stereotype and marginalize people. Some people who are the targets feel that they are hateful, cruel words. That's enough for me.
These are words I have used at some point in my life. I know now that they hurt a lot of people who are already hurt too often. To me, it isn't worth analyzing it much more than that.