What else can you do but surface alone if you've given your buddy the thumb, you're sure they saw and understood, and they refuse? I don't imagine dragging them out of a wreck when they're fighting you is very feasible.
I wonder if discussing this specific scenario during dive planning would help. If buddy doesn't readily agree that anyone can call the dive at any time for any reason and both/all divers in the group will surface together, of course, you might rethink diving with them. But if buddy agrees, does having discussed it make it more likely they'll stick to that plan in the grip of narcosis? I don't have enough experience to say, but my experience with alcohol suggests it could help. People who go to a party intending to get drunk, who make plans to, say, leave their car and take a Lyft home, tend to stick to that plan even when they can't walk a straight line. People who play it by ear have a hard time realizing they're drunk and they need to not drive home. Similarly, when I was younger and single, I always had a rule for myself that I wouldn't go home with anyone unless I'd already decided to sleep with them that night before I cracked open that first beer-- and I would share my plans with my friends to keep myself accountable and keep them from worrying. The trick to drinking irresponsible amounts responsibly is to front-load as much decision-making as possible, and have very simple, strict, and explicitly laid-out plans in place for when you're under the influence. Maybe I should plan deep dives like I used to plan college parties.
ETA:
@MalibuJerry beat me to the punch on that suggestion; two posts went up while I was putting that together!
