*laughs at the thought of Gravitation with mecha*
Possibility 1: I'd guess that they freaked out because you called yourself a homophobe. You may not have meant it in the strongest connotation, but they were probably expecting a big, classic homophobe-fanboy lecture about how it was GROSS and blah blah blah blah. So rather than waiting around till the rocket launchers fly at them, they cut you off before the sermon they were expecting.
Possibility 2: Yaoi fans tend to be a bit paranoid outside their own enclaves. They have interests that they know other people consider freakish and wrong, and they are eager to not be seen as disgusting freaks because of what they like, particularly by their non-yaoi-fan friends.
(hm, kind of like anime fans in backward areas, in a way.)
So some of them will push stuff on others just as their way of saying, "See, it's okay. I'm not a freak, see, it's not so bad. I'm normal, right?" I don't think they necessarily want you to like it; I think they want you to not hate them for what
they like.
Now, all of this is assuming that you
wouldn't throw "OMG YOU SICK FUCKS" fits on them. If you would, then really, you truly are a homophobe and I have nothing to say to you.
-- to everyone: --
However, if you just don't like yaoi, you aren't a homophobe. That's not what homophobia is. It has nothing to do with anime, or what people like to watch. It is hating
real people who are gay. Not just saying that you aren't into gay-themed entertainment, and not just saying that you don't want to see any visual representations of it. Hating. Hate is a strong word.
The iffy part is when you said it was "wrong" - that I'd have to hear more clarification on before I say anything about that.
But I agree that people throw around cries of "homophobe" WAY too often in the yaoi fandom. Way too often. They've lost sight of what the word actually means and in the process, given yaoi fans a bad name. That type annoys me almost as much as the "omg u sick fucks" side does.
Now while I think guys are laughably paranoid about this sort of thing, and trust me, I do laugh at you

- it is perfectly reasonable to say that you don't want to watch yaoi. That's your choice. Hell, I don't like mecha anime, and I try to avoid them. Generally I don't care for them. Do I shove this down people's throats and call them sick and wrong for watching mecha series? No. Do I think it's wrong for other people to watch mecha series? No, I could care less what they watch. If someone tried to force me to watch a mecha series, I'd be irritated, but that's something
they're doing that's out of line. (I'd bet they're just looking for validation - see point 2 above.)
Anyway, apply that to yaoi series and you have what I'd call a completely reasonable taste. It's when you start
a) assigning moral imperatives to a form of entertainment - "Watching this makes you a bad person"
or
b) trying to force others to agree with you
...that I would start calling you ...well, not a homophobe, maybe just an ass.
And as an aside or two:
- Gravitation is not a very good example. I like it, personally, but I would never call it Great Entertainment. It's just a cute, frothy little show. (I would think of an example in hetero anime, but nothing's coming to me. Something that's just somewhat lame fun, and not MEANINGFUL DRAMA.)
- Azumanga Daioh is not a yuri series. Sorry.

Rose of Versailles is a yuri series. Azumanga Daioh is just a show about girls. Just because there are no boyfriends around doesn't make it a yuri series; it just makes it a show about girls without romance in it. Kaorin may be a lesbian (though she may also be a hero worshipper), but one character doesn't mean the entire show has an overall gay theme. AD has very little romance in it, if at all, and personally that's one of the things I love about it. It's a change of pace from the usual romantic comedy. So, that's all for that. 8)