For the most part I think their just a bunch of angsty whiners who thinks it's cool to hate something.
Or maybe they're just rude people who like making fun of others and we just look like an easy target.
But to be honest, the impression I got talking with my first pony hater who actually identified as an anti brony was that they're all fruit loops. It was a few years ago, when I was still a somewhat heavy Twitter user. My Twitter was still mostly anime stuff at the time, but I'd been happy to have gotten caught up on the show.
I began talking to this girl and we were getting on just fine with each other and somehow talk turned to MLP and bronies. I didn't bother telling her I was one of the things she was trash talking. I was kinda curious how she could find anything to hate about a fandom and a show I had grown to love so much.
And let me tell you! That girl must have been crazy. She went on and on about how ponies were brain washing young men and she talked about how her and her boy friends were like rebels. She showed me this stupid youtube video which was clearly satire to anyone with a brain. But she was taking it literally.
It was talking about once you become infected you can't stop yourself from singing the pony music and posting the ponies. Finally I was like, "Listen, I just so HAPPEN to be a brony." I was sick of hearing crap. "Oh no," she'd said.She started talking to me like I was some kind of victim.
It wasn't long though before we we having a debate. A debate I was able to win.I did that by comparing the anime fandoms with the brony fandom. I asked her, "What would you do if someone told you that all otaku were perverts and wanted to get with high school girls. Don't bother, you would be offended because they're saying things that aren't true.
Anime fans who wear the badge of the anti brony and just recycle insults used on them as if they're new. Well they're the worse type of people!