There's nothing in the rules saying that failing to provide evidence for a belief will result in disciplinary action. It is entirely up to the discretion of the moderation team whether disciplinary action is warranted. And a lot of the time, it isn't. A lot of theists honestly believe (or at least convince themselves that they believe) that the evidence for their god is as clear and obvious as the sun. What good will punishing people like that do? If anything, punishment ends up backfiring, because of the way Christians are taught to believe that others will persecute them for their beliefs.
The problem, Zeno, is that you're basically advocating a false dichotomy. You're saying that either we need to strictly enforce the rules, or else we should write exception after exception in. The former is too rigid, and the latter is even worse because it removes even the possibility of disciplinary action for rule-breaking. Right now, I think what we're doing is a reasonable middle ground between those two extremes.