A priest who is a public sinner is one thing, celebrating the Holy Sacrifice of Calvary in the same spot the mockery of the Holy Sacrifice of Calvary is performed is something altogether different. You are not making the appropriate comparison.
Whenever the celebration of the True Mass is conditional, that is, it is only allowed as a preference (as if we have a choice in the matter) and is celebrated in the same place in which it is openly mocked with the new "mass", then whatever your interior motives are, your presence dictates your support or at least your indifference of the crimes against Our Lord committed in that spot.
It's like this poche, your father has been held prisoner in the enemy's camp where every day (twice on Sundays), they publicly punish him in front of a community of approving people for a crime he didn't commit. Every day they drag him into a lavish room only to whip, scourge and insult him without mercy until he is bloodied and insulted. But wait! Once a week, they drag him into the same lavish room and publicly hold the most honorable, most lavish feast humanly possible in his honor - because some people prefer that. Immediately afterwards, go back to whipping, scourging and insulting him as if that's the price he pays for the feast held in his honor.
This poor analogy is the reality of the situation. We demonstrate our acknowledgement and abhorrence to the crimes committed there the only way we can - by avoiding that place entirely.