fight FOR the left in primaries, vote AGAINST fascists in the general

That's how it should have worked, except that in the 2024 Democratic Presidential primary, when Biden was the only name on the ballot, we were STILL told to vote for him and only him or we'd be supporting Trump. In the primary! Voters in Michigan tried to campaign for "uncommitted" option in protest of the ongoing genocide in Gaza and how the administration was ignoring it, and they were crucified by establishment Democrats. Even Bernie Sanders distanced himself from the protest vote, saying to vote Biden no matter what. In the primaries!

I assume you mean in reference to the general last year?

That's the most recent example, yes, but you get this spiel whenever you suggest going against the party in anything beyond local elections.

I raged against the way the left brought disaster upon the Palestinians despite their best intentions.

Where are you getting the idea that it was the left that let Trump win? Democrat non-voters were for the most part moderates.

fight FOR the left in primaries, vote AGAINST fascists in the general.

The whole point of this mantra is to not split the anti-fascist vote. And what are the Democrats doing now after not getting their way? Ignore the primary and split the anti-fascist vote. The whole point of not splitting the vote is defeated when the liberals then decide to split the vote. I'm also very much not convinced that a vote for Democrats is a vote against fascism given that they just voted not to impeach Trump.