I wrote a regex that would allow things that aren't facebook, and then you said "No, you're not allowing things that aren't facebook, you're not allowing things that don't match not being facebook".

If it's not a white-list, it's at least an opposite-of-black-list.

But then why do you need the blacklist?

I refer to this post by vec: https://news.ycombinator.com/item?id=16208419

If you think you need a blacklist you should probably be using a whitelist. If your problem can't be solved with a whitelist then it's probably better solved in a way that doesn't involve a blacklist or a whitelist.