Anon, if you have a problem with it, deal with it yourself. What do you expect people to do? Tell him he's a shitbag for saying ponies don't belong somewhere? Yeah, that's going to go swimmingly. Try to engage him in a polite discussion? Does it look like that would do you any good.
I'm sorry to say this, anon, but welcome to the internet. It is a shame, but people aren't always nice here. It doesn't feel good when someone (sometimes unjustifiably) hates on something you like but those people will always be there, and yelling at them doesn't make them go away. More often than not it just makes things worse. Live and let live. If he comes to you, comes to us, to tell ponies are bad then sure, feel free to fire away, but jumping on them and harassing them makes you the bad one.
I don't agree with him and think he should grow up, but there's nothing we can do to speed that process.
tl;dr calm your tits, yo