the problem you're pointing at is liberalism, telling liberals not to vote is not going to make them less liberal.
because of your electoral system not voting is equivalent to voting for the winner, because there isn't a quorum at which an election is invalidated. take france: a 2-round system is not perfect but allows for genuine voting for small very left-aligned parties, and then eventually voting defensively later
your description of "basic human decency" is also very dishonest in my opinion: between bombing gaza and bombing gaza+venezuela+iran you can easily pick the lesser evil. while people in gaza see no difference (which is also arguable), two other countries, and people there, definitely do
i'm not arguing that using the master's tools will free us from masters, more must happen (france has many examples, again...), but it seems very clear to me that not using a tool to make a point is virtue signaling towards either peers (who are already aligned with you anyway) or opponents (who don't care)
btw i'd love to hear how this is "imperialist propaganda" and hear an opinion regarding actually addressing imperialism which is beyond "both bad" because last US low vote turnout didn't really seem to hurt the empire, or reduce the dropped bombs. there's always more proletariat than bourgeoisie so act like that