I played similar games when I ran forums, but really you're just shuffling the problem around. Bored trolls/extreme ideologues will be delighted to play cat and mouse with your measures, and will feel particularly proud of themselves when they circumvent them creatively.

In the end, you have to decide what outcome you want - using half effective measures hoping that the racists will keep it down, or kicking them out and making it clear that they aren't welcome? You can't have it both ways.