It's been a while since my biochem classes, but basically, alcohol "distracts" the liver from its normal duties. The liver can't break down all the other environmental toxins that it would normally break down, so they just sit there and accumulate, causing the problems you describe.
(The antidote for Methanol poisoning is in fact getting drunk. Because the liver is devoting all its attention to digesting the alcohol, it can't turn the methanol into toxic formaldehyde.)
I don't know for sure, but it seems to me that having one drink every day would be WAY worse for you than partying on the weekends...