You're right, gambling is not for everyone because there are people who get hot-tempered, can't handle losses, can't control themselves, etc. Gambling is dangerous for such people, they are the ones who get addicted quickly. We know that gambling relieves stress sometimes, it often gives you stress especially if you are serious about life. If you gamble, always think of your family, always set a budget that you should not exceed. It's easy to be a responsible gambler as long as you know what you're doing.
Some people will easily hurt others because of their frustrations and when you partner it with losing in gambling it will be more serious and others are gonna be in trouble while they have a kind of that person in their house or community. I remember when I had a friend and he was good at playing pools because that's one of the sports in our community that they make bets out of while playing. My friend was just a young guy and when he won big money from those big men, they made some evil plot against him while he was going home and they took his money from him after seriously beating him in the middle of the road and that's only one example of persons that are not supposed to be playing games like that because they cannot handle the heat when they lose their money.
Hmm maybe your friend didn't gamble in a casino. It could be some indoor gambling competition between him and the big men. If it's the later, then the person was actually gambling with hot tempered gamblers. Who can't accept defeat. Or maybe the other men are cliques of friends that rip off a winner's money. That's the risk of gambling with friends, off the casino settings. The casino is there to guarantee that players would be paid after winning. Without facing any dispute with fellow gamblers. However, the offline casino is also not conducive for gamblers because of such attacks. I'd say that gamblers who win early should leave the premises, while the day is clear. This type of attacks happens during the night hours.