Back when there were incidental and intentional face mask penalties (5 and 15 yards respectively), there were many a referee who would happily use his interpretation of the situation to suit his biases. I remember one defender desperate to tackle Rocket Ismail grabbing him by the face mask, and yanking his head back. The referee called it an incidental one, even though it was clear that he should have been called for the 15 yard variety.
That same game, it was either Pat Terrell or Du'an Francisco who had brushed his hand against a player's face mask, and that same ref gave a 15 yard penalty.
I don't like the "15 yard penalty for all face mask infractions" since sometimes, a ball carrier's head can dip down and brush against a would-be tackler's hand, but because of biases, it appears that there's no other choice, since they don't want to hurt that one ref's feelings.
I liken this to another masking situation to another, where at Amherst College in Massachusetts, students have the option of not using masks in the classrooms. However, if one student claims that he / she is uncomfortable and wants to mask up, then everyone has to use face masks...