To be 100% clear, I should've added this: I don't think you can suspend one and not the other as the circumstances for "banishment" are almost mirror reflections of each other. Both have been warned numerous times both publicly and privately, both attacked posters, and Zags (whether you think the attack was "less offensive" or not) attacked a poster who could not defend themselves from his words. He knew this. Zags is not an idiot nor is MM. They are both aware of the "rules". To pile on, Zags attacked the poster shortly after being reminded "not to aggravate Mediocre Man", yet consciously did it anyways.
In summary, ban both or ban neither is what I was getting at. If Mediocre Man hadn't already been suspended, I'd be leaning towards "ban neither" just because its a message board and people need to take it a little less seriously and gain some self-control and use the features presented to them, such as ignore.