It has never happened to me, luckily I go to legal places with security, where anyone who starts to be a bit annoying is politely invited to leave the premises before things escalate. But I have a friend who worked for years in a casino and without ever seeing violence, he did see people who, when they lost and with a mixture of alcohol, started insulting people and using bad manners, which was immediately stopped by the security staff.
We only gamble in places like this that can condition the gamblers in the casino and get clear legality to operate a gambling place, tight security will make us much safer from violent attacks or bad effects that occur if a gambler starts messing up in the casino,
It may be rare in casinos for someone to do that but we need to be careful, because that kind of thing might happen and make us lose money.
Gambling is a game for the ready which means you should be aware and ready that you're going to loose your money but if you think you're and lucky enough, you can pull out when you luckily wins at a round but it's sure that you must loose with a regular playing but if your mind hasn't been made up to accept the losts and it happens sudden and unexpected, you'll always be aggressive with your opposition because you never expected it.
But I hope the police only arrested them for the social violence and not for the case of gambling? Because I'm trying to understand if gambling is a legal or illegal activity there as it has concerned the police.
It seems that what happens is that many parties are involved in the chaos so that the police are indiscriminate in arresting people in the casino, so that it needs the police to see who is guilty in the end, because it could be a wrong arrest, but it seems that the place does not have clear legality so that the protection given to customers is bad like that, the casino cannot guarantee gamblers to be released for free.