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The thing is: What you are saying basically isn't true.
It is like the claim that atheists can't do art (Because evidently George Eliot never existed) and can't do comedy (Because evidently Douglas Adams never existed either.)
The leftwing tends pragmatic, we see something that doesn't work, we laugh at it (Which is one of the main criticisms behind the "Hater" label, we snark pretty damned effectively) and then we propose a solution to it.
The problem with the leftwing is that the far left voices you hear aren't the super-serious pundits, it is that those voices are generally comedians and entertainers, people whose bread and butter is comedy.
Heck we want Al Franken in the Senate.
We have this fallacy of moderation, which is outright stupid in ways which are both hilarious and problematic, where if you are "Far left" in America (Which essentially means being in favour of much the same policies which are taken for granted in every other first world country) you are somehow accused of being humourless - by the side of the aisle that seems to think of being wished a "happy holiday" as being horrible religious repression.
Because we all know the emperor has no pants but hey, he has a really snazzy shirt.
I mean, remember Chocolate Jesus? A bunch of people who believe that they eat Jesus every Sunday got miffed at Jesus being represented by a food-stuff.
The far right, on most issues, is hillarious. Humourless, but funny as heck. If they weren't, the leftwing, including the far left, wouldn't have survived this long. Tom Tomorrow is an example of a far leftwing webcomic, it is one of the brighest spots of this last eight years.
One can criticise the far left for a lot of things, but a lack of a sense of humour isn't one of them.