When I first heard of Bronies way back in 2011, I thought they were kind of weird, but otherwise didn't mind that they exist. Yes, its mostly grown ups who like a show about cartoon ponies, but, it generally isn't harming anyone, and every large group naturally has its weirder, more vocal and overzealous members, they don't represent everyone.
Since becoming a Brony all the way back in 2014 though, I have warmed up to them a lot more. I think the fandom is pretty welcoming and, although I do miss the old days of the fandom, I still enjoy being a part of it.