Remember when the vote blue no matter who people told us they were gonna move Biden left after he was elected?

Good times.

How do you bully people by guaranteeing your support for them unconditionally?

you should bully them into keeping their promises and doing more

How?

Because the US first past the post system ensures there's only two parties. So unless you can threaten one, you don't have input.

As a non-american, here in my country leftists vote for many different parties, each too small to actually pass the threshold

Civics education is bad to nonexistent so they do not learn about the spoiler effect, let alone the inevitable math behind first past the post elections. People vote based on how they think the system ought to function instead of how it actually functions.

As a non-american, you aren't close enough to notice that the people who say this are taking advantage of the situation and have been for decades.

Because it’s logically stupid and ushered in fascism.

You must have missed this part where you are making your voice heard by picking the least bad option, so here it is again:

On election day you pick the lesser evil, which hopefully all that fighting you did made much less evil.

Or maybe you're confused about how things ought to be versus how they actually are, that too was covered:

We have an archaic election system, and until that changes (work to change it), that’s the best path forward.

Fun story, my second-to-last straw with Reddit was being banned from r/democrats for saying Biden should not seek a second term (too old) and they need to hold a primary. I said this repeatedly starting about a year before the election and was called all manner of terrible things while accumulating loads of up and downvotes. When the time for a primary passed I pivoted my message to: Biden should retire (play up a medical issue) so we have the first female president and she has the incumbent bump for the election. I was banned with the message "Shut up, Biden is going to get a second term. Deal with it [inappropriate language]." twelve days before Biden dropped out.