Are you sure you did not violated the terms of service on some way? What would make more sense than telling you that you are addicted and need to stop.
2. Could be, he somehow mad and chat somethings to "Stake Support or Someone Work" in Stake multiple time like bad things stuff and other. Then, they're taking conclusion he was an addict and decide to closed his account.
Anyways... There is a chance our fellow here acted out while talking to customer service and then the Stake agent decided he was actuslly addicted to gambling and needed to be signed out of the casino for his own well-being and financial preservation, still itis very rare staff of the casino would dare to take that decision for us, instead of waiting for us to declare ourselves unsuitable to continue to gamble.
Second option mentioned by @ryzaadit might be more convincing. Or, before he got angry while chatting with Stake support team, he might have already made several deposits and gambled recklessly. So, Stake may have restricted him from gambling further. Actually, this is a good policy by Stake to ensure their customers gamble responsibly.
I am sure within the Terms of service of the casino there is an specific article or part in which it is explained the house reserves the right to restrict access to the service to anyone they assume to be unable to further gamble responsibly, so legally there is nothing to be done in this instance, when comes to whether Stake is entitled to deny services or not. However, it seems interesting how a staff of the casino could take such step without being asked for it, if this is what actually happens, means there are personnel within stake who are actually committed to the concept of responsible gambling and it is not only words being said for the sake of complying with regulators and governments with tight gambling laws.