While that's undoubtedly true, the level of trolling varies a lot so I don't think it's quite as simple as "if people can troll then they will." There's a crazy level of trolling on 4chan, quite a lot on Reddit or YouTube, and much less on HackerNews (cue troll replies to this post :D ).

I suspect that the owner, or the users, of a site are able steer how much trolling there is by incentivizing good conduct and 'policing'. If people actually value the content they won't troll, or they'll actively keep things tidy using the available tools. If people don't really care about the content (or if they only care about their relatively small corner) then they'll happily trash the bits they don't see value in.