I think you can tell him that you don't appreciate the negative language at least because that can be a form of harassment. (At least in the US) For your computer ask a manager if you can start password protecting it so you can just log off when you aren't using it. Then he can't get into your files when you aren't there. If he needs any files from you, you could print them, email them or share them via a USB.

If he isn't talking to you about work then can you politely ask him to leave you alone?

It's also not required to be friends with coworkers so I think it's reasonable to just block him from seeing updates and such on your Facebook page.