in his mind (maybe....cuz who really knows?) he doesn't WANT to quit drinking. and he's tired of getting beat over the head with it. to the confirmed alcoholic/addict, being "talked to" about the "problem" feels like getting hit with a hammer, or swarmed by wasps. it's annoying and repetitive, and they just want it to STOP. to be left alone to do what they want.
so leave him alone. let him do as he pleases without interference. get your lives separate. see him as a person with a sickness that he refuses to seek help for. know that it makes him unstable, unreliable, unpleasant.