Eh, fist fighting young isn't that surprising.

Alcohol is a poisonous relaxant. It dulls your impulse control, so for people who have trouble relaxing it's a great help.

Kind of like smoking as well. It lightly poisons you, but it's relaxing.

[Congratulations Ikki, you now have nearly flawless insight to Smoker's entire characterization. He WANTS to relax more, but he's basically too wound up and a fucking spazz, so it's so hard on him he has to drink and smoke to do so.]