Remember "Doonesbury." Might've been funny once but degraded into political polemics for the last decade or more. Once you've got an audience the temptation to use their trust to persuade them of, well, anything; seems to be hard to resist. Moreso when you have opinions that others emphatically do not share.
I can think of dozens of "liberal comics" that never tried to be funny, that were merely political propaganda in comic form. Most of Ted Rall's work, for example.
What are you talking about? The OP made it clear that it was once funny and then it devolved into partisan preaching that lacked humor entirely. Never once did OP claim it wasn't political in the first place, why would you assume that?
Bloom County? The comic that was pretty openly political back in 1983?
Sure, there were stretches of time where it didn't address anything particularly politics-related, but to suggest that it was not political seems to quite spectacularly miss the point.
I started reading doonesbury in the 80s just because it was on the comics page. I never found it funny and didn’t get it. I’ve heard people describe that it was once funny way back in the day but was never able to confirm it.
Did we read the same Doonesbury? His drawings throughout Watergate are probably some of the most famous politically charged humorous cartoons in history.
I was never a particularly big Doonesbury fan (I like Pogo), but griping about "liberal comics" seems to follow the general trend of not realizing that your politics have been on the outside of mainstream cartooning for decades.
I can think of dozens of "liberal comics" that never tried to be funny, that were merely political propaganda in comic form. Most of Ted Rall's work, for example.