While I laugh at the sheer stupidity of this person, I shall point some things out.
First off, there are people in the fandom who are like what he/she described in the petition. Are they the majority? No. The 'parent' who put this up tries claiming that he/she knew that on the surface bronies seem good, but deep down they are rape-y pedophiles.
... Wat? I think it's sad that anybody with a closed mind will take something that's out of the norm, which promotes loving and tolerating, and instantly think that it's a bad thing. He/She wants to take all MLP things off the web, even though the vast majority of it isn't NFSW or violent at all.
I'm also disgusted by the way he/she wanted to end the cartoon. So, because of an 'evil following' on the internet, you're going to try and cancel a show to stop children watching a TV show teaching them about 'The magic of friendship'? What?
This person is grasping at straws to try and get 'evidence' on the fact that bronies are 'changing' the show, even going as far to post this:
"A genuine screen-cap from the cartoon itself with a clearly visible Swastika (Nazi symbol) in it. Coincidence?: http://imageshack.us/photo/my-images/854/nazipony.jpg/"
...Really? I'm sure that the writers of the show put that in the maze because bronies told them to, and I'm sure that it is promoting the murdering of Jews and other groups. People like them make me sick.
*drops mic and exits stage left.*