To quote a Canadian court, you don't have to wrestle a person to the ground to get their keys. You call the police, and tell them there's a drunk driver on the road.
Yes, your friend gets arrested. He doesn't end up dead.
And people there knew he had at least 6 drinks, so I'm sure they knew he was over the limit. If he snuck out without their noticing? Fine, they did all they could.
By the way, if it's "routine" in their group to punch each other to unconsciousness, I'd say that friends also don't impose brain damage on friends. Someone suffering from repeated small brain injuries may indeed act more recklessly than someone without brain damage, or react to alcohol more strongly.
I still wish someone would point out what the insult to the dead is in Ebert's tweet. He WAS drunk, he WAS driving irresponsibly, and friends DON'T let friends drink and drive.