This really has more to do with hobbiest cycling culture than anything else. It in no way benefits performance. The inflammation alcohol causes is enough of a reason not to, especially in a sport where body weight is so important. I've read in the past that the effects that alcohol has on your recovery is significant enough that you're better off not working out prior to a night out on the town. I will admit that I can't find the that research now, so take it for what you will.
Alcohol is a diuretic, but your average beer is like 5% alcohol and 90% water (and 5% other stuff). Beer at 0.1% alcohol is going to hydrate you more than it dehydrated you, and a shot of 151 will dehydrate you more than it hydrates you. There exists, for any given person at a specific time, a percentage where the effects of the alcohol and the water level out. From what I've read, that percentage is typically higher than your normal beer.
When it comes to optimizing performance/recovery, I can't imagine alcohol doing anything good. Personally, I might be inclined to avoid alcohol after a hard workout where I feel like crap, but I'm not going to not have a celebratory beer after finishing a big race or something.