I guess it shouldn't really be a problem, right?
As long as they're a decent person it's not a big deal. Let them know that you aren't interested in the same stuff, of course, but also let them know you won't judge them about their kinks or whatever. It could be a bonding experience, lol. Having someone who knows you're weird in some way, but doesn't judge you for it, is a nice feeling.
Even if the content in it is disturbing, as long as it's harmless it shouldn't be an issue. If it's something morally wrong and they show a lot of interest in the real thing, maybe take that as a bit of a red flag. But it sounds like it's a harmless thing that they'll keep to themselves.