we exclude or dismiss or reflexively criticize theists who are good at partitioning

Well, yes. That heuristic tends to work, because partitioned theism is usually correlated with bleed-over into other spheres of reasoning, which can hurt people (immortal soul belief discounting cryonics thus leaving person-containing brains to rot in graves). Human partitions are never perfect, and so it is better from a mathematical standpoint to have none.

After all, we are required under pain of stupidity and becoming victims of clever fraudsters, to follow the mathematical theorems of bayesian reasoning.