Deauthorize old user on my iTunes without their Apple ID I think that my ex-boyfriend's music is still syncing with my iTunes. It is syncing via the cloud.  We both used to share the iTunes and now he has his own on his own computer (I assume).

Is there anyway I can view what users are authorized on my iTunes and delete one without knowing their Apple ID and password? Also, I do not have cloud set up so this is kind of creeping me out lol.  We have VERY different musical tastes and I'd love for these songs to stop randomly popping up in my iTunes (they are really inappropriate).
Yes! You can deauthorize any of the computers or devices authorized for your iTunes account. If you have access to a computer, the easiest thing to do is to open iTunes and go to Store -> View Account in the menus. (That is on my mac iTunes, it might be slightly different on Windows.)

In your Apple ID summary, you can see Computer Authorizations and Deauthorize All (you can easily reauthorize your own computers after this, since you have the password -- which you might want to change!) A little lower down you should also see "iTunes in the Cloud" where you can press "Manage Devices" to see the iOS devices authorized on your account and remove the ones you don't like.