"We need to let people drive around drunk on bicycles and other modes of transportation, otherwise they'll just get behind the wheel of a vehicle while drunk" is a weird argument - especially when you think about why they're presumably riding drunk on a bike: they have enough awareness to know they shouldn't get behind the wheel of a vehicle.
If someone has that kind of awareness and still thinks after a dozen beers I gotta get around town, they're really unlikely to be climbing about their 10-speed Schwinn and try to balance on it while pedaling around trying to steer away from potholes, ruts, bumps and assorted litter. They're much more likely to hop on something like their 24 HP, 54" cut, V-twin John Deere riding lawn mower and putter around in 3rd gear at the nosebleed speed of 7 mph and enjoy the vaguely cushioned seat that snugs around their fat ass, because that's a hell of a lot "safer" with less chance of falling off and wiping out and incurring all kinds of scrapes and bruises.
[Which, if they get caught operating while drunk, they're going to get busted for DUI / DWI / OWI, whatever that particular state calls it.]