Why do you enjoy it?
I wouldn't say I enjoy 'yaoi' more than other types of fanfics/fanart/doujinshi, but yaoi fanfic writers, at least (sorry ^^;) tend to be, erm, a little more coherent than the het and yuri writers I've seen. I know there's some awful stuff out there, but it's proportionately got more good fics to bad fics than het or yuri. (Gen is best, in my book, but good luck finding that.) Similarly, usually when I buy a yaoi doujinshi, the odds are better that it's not just random smut, and I won't feel like I spent money on something generic.
Taking out the obviously non-canon gayness, I think there's more of an emphasis on why characters do what they do in yaoi fanfics and doujinshi, when compared to yuri or het stuff. I think this is mostly a difference in female and male writers. As a female reader, I find more in common with what female writers write; that's not surprising.
I only read yaoi fanfics and doujinshi, and look at yaoi fanarts, for some reason–original stories with that theme don't usually interest me at all, such as FAKE or Gravitation. I do tend to enjoy series with yuri (Utena, Hen) themes or het themes (... everything.) Make of that what you will.
Has anyone annoyed you due to them liking yaoi a bit too much?
No. People who are yaoi fans sometimes do things that annoy me, as do people who like yuri and het and gen and anything. But just liking yaoi isn't a reason to dislike them. If pushed, I'd say that poor characterization annoys me the most in yaoi writers; that and cutting off poor dang Usopp's nose.
Is there a reason some guys like this stuff as well?
I know some gay and bi guys who are into it. Otherwise, because girls they know are into it, or because they like the characterization or just out of curiousity. Or, because it features some other fetish they really like, enough to ignore the yaoi aspects (well, a few people I know are like that :ninja: )
<un-yaoi characterization="" rant="">And I don't see why people say Sanji and Zoro hate each other–do people just not follow subtext well? Even with yaoi out of it, they're obviously good friends. >>;; They fight 'cause they like fighting, not because they hate each other. They'd miss the fighting and be lonely if something actually happened to one of them. Hell, they've even expressed concern for each other at times. I can't imagine seeing them as genuinely hating each other. It's like thinking Robin doesn't care about her nakama or Nami really just likes money or that Usopp genuinely thinks he's the strongest warrior in the universe. That's surface level, the actual characterization isn't like that… in canon.</un-yaoi>
And I imagine people go from "they fight but are actually friends" to "they fight and are actually lovers" because of series like Ranma 1/2, Evangelion, Trigun, early Sailor Moon, and every other series in the universe that has a canon relationship exactly like that. Some things in fandom I find puzzling, but that's not confusing at all.
People just bitch about it 'cause it's popular… just like I think fangirls push the yaoi hard because they want to gain a foothold in the previously male-dominated fandom, and lately we've been seeing the anti-fangirl and anti-yaoi push back. Eventually we'll reach an equilibrium and everybody will live together peaceably. I hope.