You need to separate various issues if you're going to have a productive discussion with United. That means treating past behavior as unrelated to your situation.

It will be difficult, if not impossible, to prove United broke the COC. Trying to go down that path will not bring a resolution without extended litigation.

In my view, the most valid question, which you raised earlier in the thread, is why wasn't there due process? Without claiming your actions were correct, because, let's be honest, your behavior was questionable and you didn't treat United like a friend, you need to ask United why they didn't provide an opportunity to resolve this issue before your account was terminated.

I would be pissed too if my account was cancelled, but you need to be calm and try to take emotions out of the discussion. Focus on getting answers from United about how and when they attempted to contact you before cancelling the account.