Again, I agree with you, but there's a history of bad DMs taking this too far. There was one small sidebar in Second Edition that talked about a god denying spells to a priest who wasn't acting in good faith, with a suggestion that you might pray for spells and wind up with only Cure spells in every slot, and some DMs took that as a suggestion to second-guess everything the character did.
When you actually are trying to play your character in good faith, and the DM takes away your powers because you make one decision that they disagree with, then the natural player response is to never play a divine spellcaster again. You never have to worry about that sort of thing when you're a wizard, after all. Or maybe you'll just quit playing entirely, if nothing you do matters and the DM is going to fiat take away your powers for no reason.
Edit: And if there was a rule that a god could never take powers away from their clerics, then even though that would place an unnecessary restriction on good DMs who weren't going to abuse that ability anyway, at least the rule would serve the purpose of preventing bad DMs from ruining the game for well-intentioned players. The only thing you need to worry about, then, is players who play in bad faith, and exploit the inability of the DM to directly punish the character for their transgressions.
i have commented in the past that IMO the keys to any relationship, especially ones as important as gods and patrons, is **no surprises** about what is expected. it seems obvious that the god, church and /or patron would have made clear to its chosen what is expected and what is forbidden and what is in between. The moral quandry tests should not be a blind choice where the player and character do not know the repercussions but instead be quandries of "if i do this, i know this will..."
Similarly, as one starts moving apart from one's obligations, there should (barring a very unusual relationship) be clues and nudges and omens or whatever provided that signal "you are going the wrong way" well before the hammer of god slams down.
IMO its a failing effort to try and handle by RULES bad gm abuses and bad player abuses because those are most often than not either inexperience issues or person-issues - neither of which can be helped by rules in any meaningful manner.