My family league is all Cardinals fans. I'm sure this post will invite replies that Cardinals fans are obsessed with the Cubs, which is probably true, but we had a problem where the Cubs were getting drafted irrationally late because most of us didn't want to have conflicts of emotion between our real team and our fantasy team. The same could be said for Ryan Braun, Jonathan Papelbon, etc., but creating a list of undraftable assholes would be subjective and dumb.
So last year, we made all Cubs ineligible. The fun part was when Chapman got traded at the deadline, and my brother had to drop him.
If you ever wondered why Kris Bryant and Jake Arrieta are only 99% owned, it's because people like me.