I guess the heart of the matter is this: Does our social contract allow one person to tell someone else that they shouldn't do something, if they find it offensive or distressing? Where do we draw that distinction?
In a word, no. There's no distinction to be drawn as so long as it's not hurting anyone, it's no on else's business.
But as Pnx said, there's a little thing called obscenity. You're fully within your right to get disgusted/etc. They have a right to get off on whatever they want; they also have an obligation to not gross other people out due to courtesy.
Lets say we were talking about media that has been digitally edited to portray a young child in a sexual situation with an adult. Not only are people generally disgusted by it, but even though it doesn't affect any children directly, it portrays something that society agrees is wrong; child pornography. So wrong, in fact, that we have created laws that prohibit the creation, distribution, and ownership of it. That's drawing a line, and it's a line I feel needs to be drawn... not to keep people from finding happiness, but because that's not a healthy or acceptable way for them to seek it, either for the person in question or for others in their community.
The two basic rules to always follow in situations like this:
1) Don't judge people for liking media you don't like.
2) Don't judge people for not liking media you like.
Note that in neither rule does it state you have to like it, accept it, etc. Just hate the media, not the person who likes it.
I don't dislike people for what they like, but I find it perfectly acceptable to dislike the things themselves. Moreover, if I cared for or regularly interacted with someone who is exhibiting a behavior I strongly disagree with (say, looking at Child Pornography), I feel it's my obligation to take them aside, explain why I feel that what they're doing is wrong, listen to their side of the story, and help the both of us come to an understanding. I get a similar feeling when I catch a glimpse at some fetishistic artwork as well; that some fetishes are signs of a dysfunction, and if they are as I suspect, I'd like to help the people who make/view them to find a healthy way of dealing with that.
To ignore something that I feel is genuinely wrong would be dishonest to myself. That doesn't mean I should hate someone because they do something I dislike, but coming back to the case of creating explicit rape-porn out of a children's cartoon like MLP, I feel I am obligated out of compassion for the person doing it to try and understand their reasoning, to explain how and why I feel that is a dysfunctional behavior, and ideally come to an understanding with them.
Does that put me among the ranks of totalitarian/fundamentalist asshats? I don't think it does, but it does seem to be skirting a fine line.