I am a strong believer that in wine lies the truth. But why does alcohol have seemingly different effects on different people in this regard?
In my observation, alcohol often removes inhibitions and reveals the default dispositions of a person.
Now, I don't think that we need to moralize what is revealed; after all, if a person is an "angry drunk", but conducts themselves with grace and tact when sober, that might reveal skill in mindfulness and self-regulation. Or it could reveal severe repression. On the surface, we just don't know, so it would be presumptuous to draw too many conclusions. (Perhaps there are some connections to aspects of emotional control?)
We might still ask whether the person ought to invest effort in resolving the underlying causes of the anger that they then manage the manifestation of. Or perhaps we might suspect that drinking alcohol is a poor choice for such a person (or that they might do it carefully).
But I do think that we need to pay close attention to how people behave and what their personalities and dispositions are like under the influence of alcohol. It can tell us a lot about how to more effectively relate to and connect with the person. (We might also consider how much the person drinks (in frequency and quantity), under what circumstances, etc.)
On a personal note--and at the risk of self-aggrandizing--I don't think that I'm very different at all, no matter how much I drink. My journey with alcohol (and relative lack of journey with recreational drugs in general) is maybe the proper subject of a different post; my point here is that, aside from things like poorer physical coordination, difficulty regulating the volume of my voice, and telling the same gods-damned story over and again (because of poorer memory?), there's nothing substantially different about my personality or disposition. I don't think I'm a "different person" when I've had alcohol or am even downright drunk. There's nothing that I'm hiding, no (substantial?) way in which I'm inhibited. I'm not really having to "manage" myself. I'm just always my true, authentic self; no pretending, no phoniness, no games. So what could alcohol reveal?