What is the ruling on one who accuses Sheikh Ibn Baz—may Allah have mercy on him—of being a "sultan's scholar" and issuing fatwas according to the whims of rulers? And is it permissible to belittle his stature, even if he made a mistake in a particular fatwa?

It is permissible to offer criticism based on argument and evidence to clarify the truth, not to denigrate individuals, provided it is done with justice and fairness, and with recognition of the scholars' due. Shaykh Ibn Baz, may Allah have mercy on him, was a virtuous scholar with immense efforts, and his mistakes are submerged in the ocean of his good deeds. It is not permissible to rely on his mistakes to negate his good deeds.