I never noticed it before, but the other day I realized the secondary effects of alcohol on a Minbari are the same as the cumulative effects of cyanide, 2d6 Con damage.
Drinking on purpose, for a Minbari Ranger, if it doesn't kill him outright, would probably be grounds for dismissal, or at least preventing him from advancing in the Ranger class until he is allowed to atone and resume his training.
If nothing else, he should lose a lot of Minbari and Ranger influence as a mechanical effect of the shame such an act should cause. Also lose Local influence from wherever he goes into his homicidal rage.
Finally if he actually hurts or kills anyone he'd be subject to legal prosecution, including imprisonment. Since I don't know any PCs who will sit still for the legal system, the fact that he fled justice will make him a) outcaste among the rangers and b) hunted by whatever government he's fleeing from and c) possibly even hunted by the rangers themselves to make up for the shame he caused them.
So basically you've got a lot of ammunition. Good luck keeping your partner sober.