Answer:
With the truth. Not just any truth, not truth that is pliable by their pretty words, but incontrovertible, concrete, in-your-f'n face TRUTH! And shove it (metaphorically) down their gullet; and make 'em swallow! Take them WAY out of their comfort zone and don't let them back in until they beg for mercy. Then tell 'em to f' off. (Leave room calmly.) Stay away for a few weeks and then pretend that nothing happened. Make them be the next one to bring it up.