You can't force someone with a drinking problem to stop. Trying will probably make things much, much worse. That includes hiding or pouring out alcohol. They will only find more. You can't yell or argue.
Alcoholism is a disease.
You can't think that alcoholics cannot be helped. Alcoholics can be helped by you letting them know that you disapprove of their actions. Make the alcoholic take responsibility for their actions. I.E. Don't lie to their boss or friends for them, don't bail them out of jail, don't buy them alcohol, don't go to parties with them, and don't allow them to live off of you financially. You can't stay with someone who is physically abusive.