I probably agree that jury nullification is a "valid" pushback, based on my ethics and based on my limited understanding of the U.S. Constitution.

But do we know of any situations where it's actually worked? My impression is that judges for some reason fight hard against its use by defendants.

I think, back in the day, it was used to get away with lynchings. Not the best example, because laws against lynchings were actually also morally correct.

I don't know of any recent examples.