umm I would hate to be against the clan on this one, but in all honesty most of the gg admins play with the rule of if you slay for a tk during the warm up round we just "SLAY"them back and that's the end of it. It's just a pretty much spoken and used rule in gg. Now as for a ban for the same reason is a bit excessive even in my opinoin.
Also, when we go into the new maps we always say to the server that if anyone slay for warmup round I or who ever the admin is that's on the server at the time will slay them in return.
and also sometimes we just let it slide depending opon how we feel at the time, but we never ban for warmup round slay for tk punishment