Huh? You're right that South Park has had a "both sides bad" approach to politics in the past, but I think you're misrepresenting how the show covered Trump. South Park was pretty much shitting on him the moment he announced his campaign and they painted him as a malevolent force that was going to ruin America, the entire time.

They kinda made fun of Hillary, but nothing beyond she's lame and a bad campaigner. And they were a little hamstrung there considering they were jumping ahead of the real life election cycle a bit.