Being drunk is just an excuse people (women included) use countless of times to explain why they cheated on their partners. Cheating is cheating, and I don't think alcohol is to be blamed for it. Cheaters should be responsible for their mistakes and not play the victim.
If alcohol makes people so unaware of what they are doing, then when 2 men are drinking together and get drunk, how come they don't end up having sex with each other? Quite simply because they are aware of what they are doing!
There's a Spanish saying - No hay borracho que coma fuego which roughly translates as - There is no drunk that will eat fire. A drunk knows that something he is about to do is wrong, but he wants to do it (usually for pleasure) and he just doesn't give a damn.
Drinking merely curtails ones inhibitions. I don't believe that alcohol is ever going to make someone do something that he doesn't want to do on some level when sober but was just afraid to do it.
The only exception where I would forgive a person for cheating is if he or she was drugged (date drug, roofie, etc) and then raped while passed out. I would see them as an unwilling victim in such a situation, but otherwise, there is no excuse for cheating!
If you are unfortunate enough to be faced with the situation of a drunken partner cheating on you and then asking for a second chance, you need to ask yourself if you can handle being the kind of girl who will worry that her boyfriend is cheating on her every time he goes out for drinks.
If you don't mind being paranoid, then feel free to go back to him. But the truth remains that he did cheat on you, alcohol was just an excuse.
Furthermore, if a man is really so incredibly drunk that he truly has no idea what he is doing, then he will probably lose his legs and kiss the ground and he will pass out. He wouldn't get an erection, pull his pants down and have intercourse with a woman.
Oh by the way, Merry Christmas everyone!