This is a good discussion. It's nice to reflect, sometimes. We should all take a little time to think about what we do and why we do it, and whether there's maybe a better way to do it.
But on this specific issue, a lot of it comes down to respect and normalization. There was a time it was OK to normalize gay (homosexuality) as bad, because it was seen as a social ill, a perversion or nature, as something that was objectively wrong. Well, now we know that's stupid. And calling stuff that sucks gay implies that gay is bad, and gay people aren't bad people. And while very few people probably WANT to be on the autism spectrum or have developmental disabilities, it doesn't make them lesser people. Less smart, or less capable in a lot of ways, yes, but not, ultimately, less human. And so when we use those words as insults, it normalizes the idea that these people are bad or less human. I don't mean that saying something is gay or retarded automatically means you personally intend to dehumanize people who are those things. But when we collectively say that word use is acceptable, it means we're kind of saying it's OK for people to harbor those feelings about people, even if we might individually know that it isn't so.
Anyone who tells you the language you use doesn't affect the way you think is full of shit, because the human brain is wired for language, and language absolutely affects our views and thought processes.
