I don't understand why you fault the guy for making you get up so that he could get into the window seat, but I get the concern that the pax could become belligerent or get sick if he kept getting alcohol.

Was on a TPAC DFW-NRT flight with a highly-intoxicated seatmate who began projectile vomiting about 30 minutes after the conclusion of the meal service. He must've gone through five rum minis (in addition to the pre-departure drink and the drinks mixed in the galley) in the first 1.5 hours of the flight. Was talking to him in the lounge before the flight and he was pounding drinks there, too. He probably should not have been served any more alcohol after the second round.

Maybe your FA felt that he wasn't a problem, or that giving him drinks would keep the peace. Maybe his drinks were getting increasingly more "watery." I've been on flights where I've found my drinks getting increasingly more diluted after I've been through a few.