It's often said that the star players receive preferential treatment that other players don't. Former referees have confirmed this, stating that people in the stands come to watch them play, not to see them in the penalty box.
The Canadiens don't have a big star, so no preferential treatment. This was evident in the game against the Edmonton Oilers, with two penalties called against the Habs in the final minutes and overtime.
Monday night, in the game against the Avalanche, many believe the Canadiens were once again on the receiving end of preferential treatment. On the sequence leading to Rafaël Harvey-Pinard's goal, Nathan MacKinnon clearly tripped Jake Evans. The puck was right there, so the referees undoubtedly saw it.
It's infuriating to see penalties called for minor infractions while blatant actions go unpunished. In this sequence, it's simply embarrassing for the referees, who should have called a penalty, even if it involved MacKinnon.