First of all, I'm sorry for your loss. Sudden accidents like that are always tough. I lost a very close friend a couple years ago to a guy going home from the bar, at 80 mph (in a 25 zone), in the middle of town. T-boned her in an intersection, she was getting off her shift at the hospital, from the ER... He wanted to get home to call a girl he got the number of. (and yes, he was WELL beyond the legal limit)
But yes, I do believe it is fine to drive after a SINGLE beer. The guy fell asleep because he was tired and should not have been drinking. Accidents like that happen all the time without a single drop of alcohol involved. You would not find a single court in the land that says a normal driver is impaired after drinking 12 ounces of american beer. The alcohol did not cause it, lack of good judgement did.
And second, its call a straw man argument. Go look it up. Your argument is 100% invalid and pointless in this discussion, you can not debate one topic, and then try to use a completely unrelated but valid point to solve your first argument for you.