Ofc you should be happy when you win. There is just this assumption that na players are better individually and "one of the best players in the world" even if they play vs astralis who are debatably better individually depending on player. Maybe it is because finnish are very modest. We think it is bad karma to celebrate before winning and talking highly of your own team as if you dont take opponents seriously.
I have heard interviews from na players and they are respectful. Majority of the fans on the other hand are so cocky that i instantly want their team to lose