If they aggressively defend them, it annoys me. But that's for any kind of fan-shipping, not just yaoi and yuri. People have gotten upset with me for shipping one of my OCs with an official character. Other people have told me it's fine as long as I don't get overly defensive about it. Personally, I have better things to do than worry about the relationship status of a cartoon character, know what I mean?
Nothing pisses me off and ruins a fandom to me more than a shipping war. Except for the whole Twilight Sparkle Alicorn debate among the Bronies. And don't get me started on the Equestria girls fiasco ><
It'd probably be an insult to someone who wasn't gay. But then again, MLP isn't focused on relationships, so when it gets right down to it, the sexual preference of any of the characters is completly irrelevant (aside from the characters who are already married, i.e. Shining Armor and Princess Cadance, or Mr. & Mrs. Cake). Kinda like how everyone is saying that Ernie and Bert from Sesame Street should be gay, and that if they're not gay, then they're sending an anti-gay message to children. I completely disagree. Just like MLP, there is no focus on relationships, so they're neither promoting nor speaking against homosexuality by not making Ernie and Bert gay. Know what I mean?
Oh, I knew it was focused on the relationship of friendship, I meant relationships like love and marriage and things like that. Aside from who I mentioned before, MLP doesn't focus on those types of relationships. You don't know who Ernie and Bert are? Well, to answer your question they are from a children's show called "Sesame Street", along with Elmo, Big Bird, Cookie Monster, and other characters. Ernie and Bert are two characters in the show. They are roommates and good friends, but there is a big debate going on about making them gay.