They'd get to stick around if they followed the rules. Furthermore you'll notice, if you read through the old topics, that most creationists simply flee. They don't stick around long enough to be suspended, or even answer the rebuttals put to their arguments.
We can't control their behavior, of course. But the admins don't tolerate repeated infractions of the rules. Suspension isn't permanent, anyway. It's over anytime the suspended chooses it to be.