See: dynamics of older and younger siblings.
The idea "well, no one can punch!" is rhetorically clean, but pragmatically problematic. There is a long history of people who had to punch up to break a ceiling that should never have existed.
So, while it looks like punching up, having a group "punch up" at someone is actually punching down at an indiv.
But it's near impossible for a collective group of people to perfectly balance their outrage in just the right way, at precisely the right people, for exactly the right amount of time.
We just accept the tradeoff that progress is messy.
You see massive disconnects.
But still, people "punch up", and progress gets made.
Assuming a person's privilege based on race, gender or other immutable characteristics is imprecise and counterproductive.
A minority can complain about a majority, but the reverse is frowned upon. The amount of "frowned upon" is amplified by the degree to which the minority the majority impugns has been historically hurt by similar opinions.