I even suggested on a certain thread that all the clan(s) be banned, in case of banishment of one of the “players”.
That would make a good cleanup. And I don’t think the banned “Oh darn, I didn’t know I was playing with such a player” players will come and complain on the forum 
Just ban the player, the group, and the clan.
Problem solved? No? But it can help.
Solo (SFF) is another problem