Really?! You call that arrogance?! Really?!
The kid was simply stating a fact and backed it up. It's not arrogant if you back it up: it's called having supreme confidence and being a champion.
My sig below reads "Athletes today are scared to make Muhammad Ali statements". Seth made a statement and backed it up. Only the elite are capable of that, and Seth is one at least at the junior level right now.
As for Kassian, I do not think his actions were arrogant at all. It's his home crowd and he's trying to get the fans back into the game after the Oilers tied it up.
Athletes don't normally claim it before backing it up though....
Ie- Ali even though he backed it up was seen as arrogant even though he proved it.