Well, it appears you violated the Terms and Conditions you agreed to when you made the deal to promote the casino, by signing up under your own affiliate link when they explicitly tell you that you cannot do that. You agreed to those Terms and Conditions and I assume you would hold the casino responsible if the casino violated them just as they are holding you responsible for doing the same.
Furthermore, they claim you have never sent them any players, which is at odds with your claim that you are promoting this casino. Have you sent them any depositing players?
After you took the bonus and lost, you wanted out of the bonus program, which obviously is not fair to the casino. If you had won with the bonus I suspect you would have stayed in the program, no? The screenshot you posted advertises 24/7 support with a phone number, not an email address.
Maybe I am not understanding the whole story but I don’t see how the casino did anything wrong.