There are way too many stories that I've seen in the recent years about harassment on the internet, which equally depresses and disgusts me, and what's worse is that anything helping with those issues are slow to take effect or non-existent.
In the past, I tried a lot of tactics when it came to bullies, from ignoring to retaliating against them (the latter tends to backfire horribly, not so much because of what they do, but in most cases, you come off looking as the one in the wrong, either for being the bully all along or for 'white knighting'), and it's, in all honesty, a frustrating situation all around. The best nugget of wisdom I can give is that people do mature (or if you want to be cynical about it, lose interest).
As I mentioned before, bullying does stem from chain reactions, and it is sadly a facet of human behavior. If one person is picked on, they can (but this doesn't necessarily mean everyone will) go on do the same to people that they deem as 'weaker'. But in my opinion, liking My Little Pony is far from weak, in fact, being open about it as a teenager/young adult male takes a lot of the qualities the show does promote (the courage to be yourself, regardless of what others will think, as an example), it would just be nice if they could take in some of those lessons as well, like acceptance and tolerance.
I also think some of the MLP-related bullying does stem from some of the negative connotations with brony culture, which is horrible, because "bronies" have probably been some of the nicest people I've come across, especially compared a few of the other fandoms I'm into, or were into at a point. I just wish more people would take the time to talk to people and see that.
After all this rambling, I don't feel like I was much help, though.