There are two basic approaches to your Q and the whole subject of alcohol and addiction in general is complex.
But alcohol is a disinhibitor so that’s why those who can normally keep their anger at socially appropriate levels, kind of explode when drunk. It’s kind of like a car going along without brakes.
What the anger is about varies from one person to another but the only real solution is honest self evaluation which can be helped greatly by regular time with a competent therapist.
But addicts and alcoholics are not exactly very good at self honesty and dealing with reality or they wouldn’t need the escape which alcohol provides.
That’s basically what all addiction is about (whether it’s alcohol or something else) it’s the substitution of an alternate reality for the one that the person can’t or won’t deal with.
That’s also the difference between people who become addicted to narcotic painkillers and those whose bodies develop a physical tolerance but can eventually discontinue using them at all.
Some people take them to deal ONLY with the physical pain for which they were prescribed. Once their physical pain dissipates (through time or effective treatment or surgery) they have no problem weaning off the pills. As a matter of fact, they want to as soon as possible because they don’t like the mental side effects of these drugs.
The addict, on the other hand, is using the painkillers more for the OTHER pains in their life (emotional, mental) and keep wanting to increase the amounts to get the same effect.
That’s also why some people can drink fairly regularly but not become alcoholics. They don’t allow it to interfere with the important things in their lives like job duties, safety, and personal relationships. It’s not at the top of their priority list the way it is for alcoholics.
So basically, alcoholism and addiction are all about poor coping mechanisms for handling life’s challenges. The drug or booze becomes their crutch to get them through emotionally and becomes the most important thing in their lives and they can’t function without it. Thus they lead very crippled lives and it effects all of those close to them. Friends and family and responsibility start to slide down the priority list.
And with angry drunks, people around them get past the toleration point for it more quickly. So sometimes they wake up to the fact that they’re alienating everyone and decide to make changes. Others just continue to lead sad angry and isolated lives.
About the only choices for those who care about them boil down to cutting them out of your life or getting others together for an intervention to get them into treatment. That’s about it since adults are free agents and you cant live someone elses life for them.