I'm pretty sure the mechanism is: backing down from your position of power, apologising, being quiet in the community, and finally reintegrating once you've shown that you've learned from your past mistakes. Prison is (ideally) a non-voluntary version of this, and many countries rely on prisons to rehabilitate people.
On a smaller scale, I've seen this happen in friend groups: friend does bad thing, everyone tells them they've done a bad thing and that they need to absorb that, friend disappears for a year or two, keeping in touch with some of the group, and when they return they have the people they stayed in touch with to vouch for their personal improvement. There's plenty of movies where this happens to the protagonist near the end (although usually the format mandates that their transformation takes less than a year).
> [...] RMS would rightly be considered a saintly figure for his contributions to the world.
Good people can do bad things; the best people improve from them (see the above movie-protagonist analogy). Returning someone to a position of power without adequate evidence that they've changed their ways means that they have no personal incentive to put in the effort and improve themselves - they can return to the status-quo, which means the people that were disadvantaged before remain so.
> No, the point is to exercise power, to show any straight white (or white-presenting) male that they are vulnerable, [...]
People do use power when they attempt to de-platform someone, but I don't think that it's being used here for the sake of it. This person has done some crummy things, and refusing him his position should be a wake-up call to him that he has misused the power he was trusted with (this is the "everyone tell them they've done a bad thing" step in the friend-group analogy). It would also prevent this person from misusing the position's power further.
Making people feel vulnerable might sound bad at first, but the alternative is that some people are invulnerable, which (to me) is a terrifying prospect. Being able to do anything with no social consequences would allow people to serially commit to doing horrible things, without ever losing their ability to continue doing them.
> [...] and to ensure that more and more of us hide our heads lest we be the tall blade of grass that gets the scythe.
I'm not totally sure how this metaphor works, with respect to what the length of a grass blade represents. If it represents how poorly the person treats women then the metaphor works, but doesn't really seem to support your rhetoric.