They thought making fun of republicans, catholics, rednecks and other right wing stuff was funny in the past seasons. Why can't making fun of left wing stuff be funny?
That is a pretty transparent argument. The reason why they think those things is because they are the ones being made fun of now. Shoe is on the other foot and all that jazz.
What If they didn't find stuff like funny either? I know people in this very thread who are being passive aggressively referred to as whiny liberals that weren't fans of earlier seasons either, or the show in general. And yet you're assuming why they take issue with the show instead of listening to what they have to say.
You're just shutting down criticism because it's a show you like.