I don't understand any reasons to kick outside you make stupid things like open the gate (siege team) or fall down the ladders (attack team)
Leeching (afk in siege tower, run to the edge of the map, stand at flag all round, looking for a small unknown place (many of these), etc), intentional teamattacking, opening doors, blocking the way to the flag to fellow defenders, block ladders as attacker, kick people down walls. These ones come just off the top of my head, I am sure there are many more