The only reason not to do so is the vanishingly rare chance that democrats turn a red state, which is basically the exact same argument they use to tell people to vote blue no matter who, but more compelling because it’s not typical genocidal am*rican politicians they’re voting for.
What are they going to do? Tell you they want to vote for a war criminal on principle? The positive political pressure of having a somewhat popular socialist party far outweighs the small chance democrats could have won (and this is even from their perspective, that the democrats winning would fix everything somehow)
I like telling libs to register as Republicans and change the GOP from the inside if they really believe in the efficacy of entryism and reformism since they won’t shut the fuck up about “not making perfect the enemy of good” and whatever liberal bullshit they say to support a genocide, but a woman of color led version