It really is no excuse:
Intoxicated people have much greater control over their behavior than generally recognized. For example, in those societies in which people don’t believe that alcohol causes disinhibition, intoxication never leads to unacceptable behavior.
Research in the US has found that when males are falsely led to believe that they have been drinking alcohol, they tend to become more aggressive.
…
So it isn’t simply a case of “the alcohol made me do it.”
The article goes on to note that in tests drinkers performed as well as sober people if they were offered small rewards.
It doesn’t take a genius to realize that absolving criminals from responsibility for their actions for any reason whatsoever is going to increase crime, especially violent crime. Until 2003, when our most senior federal court here in Germany decided otherwise in a fundamental test case, intoxication was generally considered an extenuating circumstance; in cases of extreme intoxication defendants could literally get away with murder. Quite predictably, habitual drinkers who planned to murder someone, usually their wifes or girlfriends, made sure that they had blood alcohol levels upwards of 0.2 percent before they did the crime. Especially galling was that this very obviously required premeditated planning, but bleeding-heart judges were only too happy to let them get off with a slap on the wrist: “The poor man, losing his wife in such a tragic manner!”
Googling didn’t really tell me how the issue is handled in the US, it seems that the various states have quite different laws.
At any rate, in my personal opinion it should nver be an excuse. There may be some rare cases where somebody loses control under the influence after all, but it then is their personal responsibility to keep their hands off of alcoholic beverages.