He did this during a post-match interview on the Hearthstone stream. This wasn’t some personal political statement outside of his participation in the game.
Correct. It was a personal political statement made during his participation in the tournament. And I agree with jcranberry and PeterisP: the rules do not prohibit that.
It looks to me that it was written with stuff more in line with white supremacy advocation and stuff like that in mind.