I think the important takeaway here is that you may hammer R's all you want, but if you want to rely on the left electorate, you have to serve the left electorate.
So the fight really is between "let's at least hold blatant fascism" and "let's tech Dems to listen a bit so that on their next election they would actually cater to the left instead of being lesser evil".
Because right now Dems are just that - lesser evil that doesn't care to align with the leftists.
I have no balls in this game, I'm not even a US citizen, but I see the point they're trying to make.