I just can't get why he said that getting a free money will become a debt?
Simple as that.
I agree with you and also admit that gambling should only be for fun and not for making money. If you become addicted of gambling then it is hard to quit because gambling is like drugs addiction and you will not be able to leave it easily. Gambling should be in limits and if you cross your limits you will be in debts because winning chances are rare.
Gambling can be good for fun and good for making money as well. If you are a person that looks for various ways to earn, you can make money with gambling and you can also make by not actual gambling but getting referrals and sign ups through a casino. You can make money through it and you can also take the advantage of it by just investing to their bankroll.