>why do people who generally recognize that Bill Clinton was a
>sexual harasser and is an accused of rape, keep bringing up
>voting in the 2016 election as a cudgel to people who sat out
>the election?

and because in a dirty game like politics, where the stakes affect all three branches of government, there is the need to compromise.

sitting out is brought up as a rebuttal for those people who sat out and are openly outraged, terrified, despondent, etc.
their refusal to pick a side where they knew what certain stakes were played a role in that.

if someone who sat out isn't really that put out one way or the other because they say damn the system, then cool. but don't come with this powerless rage just because the power wasn't properly aimed.