Reddit, what is the legality of websites hosting grey area content? Specifically, Bestiality.

There are quite a few websites who host images and videos of real life bestiality. Is this legal? Does the "user is responsible for all content uploaded" clause in the ToS really make the company safe?

I'm asking this because I'm thinking about launching a website tailored to a specific small/niche community. However, some people closely tie this particular community with bestiality, and there are plenty of images of the two together. Should I launch this site, I fully expect this sort of site to draw people who want to post images of bestiality in the public gallery (which isn't the main aspect of the site, but one of them).

What is the legality behind this? Am I completely on the hook for things people post, even with clauses in the terms of use and on the upload page? And for that matter, what clauses WILL protect me from this sort of thing?

Has anyone actually ever been prosecuted for this kind of thing?

Again, I do not condone, have an interest in, or specifically want bestiality on my website. My website is not bestiality related. However I fully expect it to be uploaded by someone at some point. Just wondering if I should be on the ball to delete these things, or if it's harmless to leave them up.

For the record, I'm in the US.

Thanks, Reddit <3.