My friend—let's call him "Ensign Harry Kim"—started watching MLP earlier this year. Ensign Kim doesn't get out much; he's perennially unemployed, ostracized from most of his family and previous friends, and barely skates by on the proceeds of plasma donation. I don't blame him for wanting to share his interest with me. I get that: when you're really excited and enthusiastic about something, you want to share that with your friends, even against your better judgment; even over their protests that they have no interest in this. Don't get me wrong; I've enjoyed the episodes I've seen, but I don't want to be coerced to watch more, much less read through all this MLP fanfiction you've downloaded. Hell, I'm still trying to sort through all the "Harry Potter and the Methods of Rationality" fanfic, 3.5 D&D character builds, and these furry homoerotic short stories you wrote. I don't have time for this.
Long story short, I think at least a part of the brony phenomenon is that "Friendship is Magic" is a hall-pass for gamer-identifying guys to indulge their whimsical side, but it looks like you guys have established that already.