To use unethical, illegal, or injurious means; be deceptive and tricky; chicane: When he started in politics he didn't mean to play dirty
[1940s+; the related form play dirt is found by 1908]
"My dear General, when you play dirty tricks it is necessary that they be successful!"
But be careful, because if Jupiter Equilateral is involved in it, they're going to play dirty.
Now what is this but making use of religion to play dirty politics?