If you were the casino manager would you fire the casino worker for interfering with your business or would you ban the gambler from visiting the casino?
He already do what is the right thing as a human but it's not professional for him to do that while he is working. He has alot of other time to tell that guy to stop going to a casino but he choose to do it on the casino itself while working so I don't think he will be fired but disciplinary action needed for him