So I don't know for sure but I think you telling him to deal with his ban is enough to trigger the forum guidelines, even though you might not see it as an attack, it is to some people. So in order to keep the peace they might have a very tight area on how far you can go.

Another way to look at it is that someone could take you telling them to deal with it as you saying that they deserved it and shouldn't even have the opportunity to ask why they got banned or something along those lines. Which in turn would trigger the forum guidelines if they are sensitive enough.

I don't exactly have the answer to why you where banned but I am sure Grey Havens has some justified reasons for temporarily banning you