Well, for the paladin and ranger, just say either "yo, don't take clerical spells," or just swap for wizard spells. For the wizard, its not that they get a cleric spell, its that they get a new wizard spell from "x list of other spells". With those spells not being granted by gods, its now a list of obscure wizard spells.
Or, y'know, say to the wizard too, "to, don't take clerical spells"