Starfox
Hero
But a fighter does lose any abilities granted by a diety, just like a paladin. And the dm is not "stepping in." The dm is merely playing the part of npcs just as he's always done. Insult the innkeeper's daughter, and you're liable to lose your inn privileges and be sleeping in the street. Insult your deity and lose your spellcasting privileges. If a paladin jumps in a lake, the dm is not punishing him by declaring his lantern no longer works. Nor is he punishing him by stripping his powers after he burns the orphanage down. He is merely adjudicating the npcs of the world's actions. Actions have consequences, else why even play? If a thief gets caught stealing the crown jewels, should the king just shrug and do nothing? It's the same premise.
Is a deity really an NPC is a setting? If so, it is unique for divine origin characters to have their power completely dependent on an NPC. (Except possibly for the Warlock 3.5, not really familiar with that). A wizard apprentice can find another master, a thief can change guilds. And a fighter can multiclass or get magic gear that allows spellcasting. None of them have the dependency on a GM-controlled agency divine characters (and especially the Paladin) has.
It gives the DM an unprecedented amount of control over the character, which I guess is part of the reason many players shy away from divine classes.