OP never said anything about you or I individually making Harris not do genocide. I mean, it's a communist board, we must talk about people as individuals because they are, on many levels of analysis, individuals, but political action lives and dies by group effort.
Me skipping a vote for Harris (or Trump) tells that candidate nothing about why I didn't vote for them.
Nor did OP say anything about not voting, which is silly for the reason you describe. However, and this is again the doctrinaire response, voting for a communist does tell the mainstream candidates quite a lot about why you didn't vote for them, even if that communist candidate cannot win that election.