I really, really don't understand the whole "Bronies vs. Anti-Bronies" conflict on the internet. Sure, I guess it may seem weird for grown men to watch a cartoon whose intended audience is little kids, but it wouldn't be the first time that has happened. Part of the success of the Warner Bros. animation studios in the 1940s and 50s was the fact that the Looney Tunes/Merrie Melodies cartoons had broad appeal well beyond the child and teenage demographics. Animators and TV executives aren't stupid--they want to maximize their viewing audiences, and they know where the money is.
As far as MLP:FiM itself, I think it's...okay, as far as modern Western animation is concerned. It's a well-produced and reasonably well-written show. It's not really my thing, but I'm sure that some people here would consider me a weirdo for still liking Animaniacs and Regular Show at age 32. Liking cartoons as an adult does not preclude one from being a functional, educated, productive member of society.
Honestly, the only negative thing that I could say about Bronies is that some of them tend to be a bit too enthusiastic, bordering on obsessive, about their fandom. But every fandom has those types of people, so it seems pointless to single out Bronies for criticism on that front.
On a final note, let me just say that anyone, past or present, associated with Andrew Brietbart is a fucking tool, and is deserving of nothing but scorn and mockery.