So once you stamp out the big, easily measured objective forms of oppression, you find yourself on a treadmill where working harder and harder to suppress the little stuff doesn't do any good. Each generation feels that they're as oppressed as the one before, even if objectively things have changed dramatically in their favor. The only way off the treadmill is for the 'victim' group to stop viewing every experience through the lens of imagined oppression.

Do you seriously think that proves we shouldn't try to stop what we asses to be "oppression"? Diminishing returns do not equal zero returns.

You either missed the point of the grandparent, or are missing some of the prerequisite concepts needed to think clearly about this subject, it seems to me.

I'm quite certain that Multiheaded is well aware of the law of diminishing returns and its implications, and has a fairly good grasp of how to do expected utility evaluations. Everything else you said in your post was, AFAICT, already all stated or implied by the grandparent, except:

Another important factor is the fact that those who consider themselves victims will never be satisfied, and indeed this whole campaign in their name quickly ceases to improve their lives to any measurable degree.

I find this claim dubious. I consider myself a victim of the oppressive historical patriarchy and dominance of gender-typing, and yet I'm fully satisfied with the current, ongoing efforts and measures that people all around the world are doing to fix it, as well as my own personal involvement and the efforts of my close circles.

You find yourself restricting freedom of speech, religion and association, creating an expanding maze of ever-more-draconian laws governing every aspect of life, throwing out core legal principles like innocent until proven guilty and the right to confront one's accusers - and even then, success is unlikely.

Those are not particularly convincing examples of Good Principles that we'd want to have in an ideal society that we should aspire towards. My own brain is screeching at the first three in particular, and finds the named legal principles crude and unrefined when compared to other ideals to aspire to.

Each generation feels that they're as oppressed as the one before

That has not been my impression. Some advocates might think things are as bad as they were 5 years ago, but I'm not aware of anyone with influence who thinks things are as bad as 50 years ago. Or any advocate at all who thinks no improvement has happened in the last 500 years.