I hadn't consciously thought about it before but . . .

This is actually really bad satire. Democrats govern well. Their big problems are civility politics, their inability to fight for what they want, and the use of identity politics. Better satire would have been signs that say something like "don't be aggressive" and "more black people!"

The banners seem constructed by people of the opposing parties...

Democrats don't hate life, and the inability to govern lands squarely in the lap of Republicans.

There's a third party against that duopoly, already on your ballot.
Not genocidal but Green.