One reason I think is that Tapastic is still young. I've once in awhile come across a comic or a user that were a bit ready to jump at the first offense, but those kind of accounts are few and far between around here. So the site is pretty much hate-free. For now.
Also, through the forums and the comment section, we creators are what to thank for this almost hate-less site. We severely want this community to be accepting and open to all views, and despise openly offensive content or comments. We are willing to work hard at this, that way more people can be brought here without much worry of trolling or haters.
Another reason why I think this is possible is just the way the site is designed. The friendly looking mascot, the user-friendly interface, the easy-to-upload program, and the way the popularity works, (not based on up or down vote, just likes), all benefits the creator. You are urged to give love through this. If a comment is given, it benefits the creator. There is no negative side.
So for however long, this site is a diamond in the rough. It might find some new obstacles in the future, but we creators (and the staff as well) are here to make sure that doesn't happen.