I'm just curious on this one. Especially consider that nobody has died from Sharptooth attack in the Great Valley in over 100 years until that time and that everyone also might suspect Chomper is harming others too.
Also, note, Chomper got away. They might want to take this out on Littlefoot, particularly a hothead Topps and a mourning and angry Ali's herd.
Another thing I thought of, is, knowing Topps, would he be suggesting lifetime banishment, or would he be likely, especially as he gets hot tempered and also seems to have beefs with Longnecks, want the death penalty for our Longneck hero?
This part would be the climax of one of my stories so I need a reason to get Littlefoot out of the Great Valley so he can go to the Great Divide and see his mother's grave and stuff. Also, it adds to drama if he's banished and finds, or feels, that killing Chomper, his longtime pal, may be the only way to get unbanished.