Hear that? It's the greatest thing to ever happen. No hyperbole there. Penicillin? Nah not as good. The Automobile? Nah not as good. All of modern medicine? Nope ponies are better. The internet? Worthless without ponies.

I think the image Sal posted is pretty good explanation.

I was trolling the MLP thread since March. Even going as far as calling Bronies little girls. I watched the first season about 3 weeks ago and claimed it was shit and that the brony community was creepy. I stopped watching it for a week... but watched and finished the second season recently. I dunno how it happened but the show grew on me and is honestly one of the best cartoons I've watched since Futurama.

It's counter culture. It's like some sort of rebellion for people with nothing to rebel against. Instead of yelling "Anarchy!" and marching on city hall or tying themselves to a tree to prevent deforestation, the men of today choose to rebel by watching a little girl's cartoon and saying "Hey! Look at me!". It will pass soon enough. Just ignore it.

Why you should be watching MLP:FIM

I invite you to the official thread, where we've had this debate before- and I'm more than willing to have it again.
My short version for now:
It's genuinely an entertaining show- I, as almost every other member of the fanbase, started as very critical of the series (I mean come on - it's My Little Pony :S), but being the open minded and curious person that I am, I decided to watch a couple of episodes as an experiment; to see whether the show could be considered good in any way, or whether the fans were only watching to be ironic. I discovered a show with fantastic characterisation, good animation and great music; I watched a couple more to make sure that it wasn't a fluke, and I found myself wanting to watch more. It was around this time that I created the "Help! Am I a Brony?" thread.
Some people in there suggested that I looked at some fanart etc., and I did- I realised that the community is so dedicated and fond of the MLP:FiM series, that their work is better than what I've seen almost anywhere else. It inspired me to watch a few more episodes, and eventually the creation of the MLP:FiM Official Thread on VGChartz, which was intended to be a place for fellow fans of the show to share their thoughts and feelings without being lambasted by other, more shallow, members of VGC.
This thread developed, and I genuinely believe that the VGC MLP thread contains some of the best people on the site - not because they watch Ponies, but because they're great people. Not only this, but I feel that watching the show has inspired me to become a better person myself, by recognising the benefits of kindness and friendship - it sounds ridiculous, and maybe it is, but that's what I believe.

Wait... you are a Brony Ryan? :o I'd thought I would never see the day...

Well that's trap. Not long ago I was behaving the same as people who claim how silly it is to watch MLP, just like d12. Until I was challenged to watch it and all reality was destroyed and I started puking rainbows. The show literally shattered many mental barriers I previously had. 

That made aboslutely no sense but I'm not really surprised that it doesn't.

The show and the characters are much deeper then they appear. Current pop culture can be found in many episodes. You must have an open mind and not assume that just because a show has pink and blue ponies, that it is just for little girls.

Forget everything you ever thought you knew about My Little Pony. This show is completely different. The director wanted this show to be enjoyable for kids as well as young parents (20's-30's). There are comedic scenes that only children will find funny, and there are scenes that only more mature audiences will find funny.

That's why it's awesome

IMO For grown men to like this its a fear of adulthood and the responsibilities that come with it. Hence the regression to children's programming.

Now why a "girls" show is another question that I cant begin to fathom why grown men like that. Now I want to be delicate here.....but lets just say I think if your a grown men watching My Little Pony......it would be relatively safe to predict that their quality of life may not be as high as the average adult.