They have already acknowledged their mistake and blamed their database and said it had errors. While you might see this as a small mistake, we all are not aware to how many problem gambler Stake is doing this. Problem gamblers are probably their main source of income and they should not target excluded account for their promo mails. There is no casino that is allowed to do this.
I get why OP is making a big deal out of this. Based on the response of the casino, they had little to no remorse to the impacts of even the simple error of sending promotions to gamblers undergoing such situation. These gamblers are vulnerable, and OP for one, perhaps felt being taken advantage for his weakness to temptation brought about his condition.