He made a private conflict public in the forums. Whether he hosted, linked, or otherwise indicated anything offsite is irrelevant. He still broke the forum rules by publicly making a personal attack against another forum member. When PMed and given the change to stop, he then continued to post again anyway.
He was warned, he decided not to listen, so we banned him.
If abiding by rules that provide respect for all members in these forums is too much for you, perhaps this isn't the best forum for you to be in. But from my perspective, our greatest growth has come from the fact that every member and every question or problem is treated respectfully here which is more than I can say at many other Mac forums on the net. Mutual respect at all times has been the bedrock of this forum since the beginning.