I think the point is that yes, having a notice that your posting privilages have been revoked would be nice. That's a given. Is it neccessary? No. Anyone with any sense and knowledge of "acceptable behavior" would know the reason for the actions of the moderators. It doesn't take a brain surgeon to put together the action of posting angry raving posts and then subsequently getting disciplined for it.
Would anyone agree that there is ever a justifiable reason for verbally assaulting someone else on a forum?