Considering how casually the word "Nazi" is thrown around these days, perhaps that should indeed be a matter of concern.
My point is, this is only an issue because FB wants you to continue to cede the power over your feed ( your attention) to them.
No one on my feed, of any group or any friends, are holocaust deniers.
So I would never see any such content, if my feed was fully under my control, correct?
That's fair enough. If FB was purely what it originally was - showing updates from your own connections exclusively - then of course a measure like this would be nonsensical. Only people who were directly connected to people posting it would ever see it (and many such people would be beyond hope anyway) and there would be no need to stop any kind of content "propagating" since no content ever would.