He didn't do anything that violated their terms to terminate an account and after all he don't really matter that much to the casino's perspective, he will be given attention only again if he needs help or violates the terms. Until then they have a business to run and it doesn't seem to be worth going after everyone who tries to bully/false accusations against their reputation.
You do have a point, but they could still pull the plug on him if he harassed them a whole lot more on their site when compared to his erratic and short-tempered behaviour with them on this forum.
There is always a limit to which casinos can put up with their customers basically.
We saw just one on the forum on that day but the support team maybe handling a hundred similar cases every day so they know how to take care of it and its better for them to play by the books so the individual can't blame the casino if the mistake is from the user end but if the casino decides to terminate an account just because they didn't like the way the person talking then it can be seen as authoritative which is not good for customer based business.