Maybe the theory of modern men being feminized by the media is true.
I think it's more of a rampant childishness. The internet has a good sense of irony, and shows like mlp seem to latch on when you have a large group of adults watching (with amusement, I'm sure) a show aimed at younger audiences. Most of the mlp things I see reference nazi reich allusions in the large princess horse who rules the kingdom, murderous insanity in some of the characters, rumors of a lesbian character, zebra racism, puzzlement over how animals without hands could build houses, and other good-natured ribbing. It's like a silent mystery science theater 3000. I figure most of the older male fans get a kick out of misinterpreting the innocence of children's shows. It's not my cup of tea, but I have done the same thing with some anime shows or manga aimed at younger audiences than myself.
Didn't the same thing happen with spongebob squarepants?
I would guess people have a mocking sorta affinity for the show. I don't know how seriously the audience takes it.