The left and 'earnestness'
The problem seems to be a desperate effort to attach meaning to every gag - just listen to such tiresome old marxists as Jeremy Hardy and Mark Steel on Radio 4. Every sinlge bloody routine must have as its centerpiece how evil the States is, or why all Tories are embodiments of evil. Delicate allusions are not allowed, presumably in case someone, somewhere hasn't heard that George Bush is really stupid.
Good humour doesn't have to have a message - it's better when it doesn't. Leftists often shoot themselves in the foot over this by their insistence that there are some subjects about which it is impossible to joke. Inevitably, these are the subjects about which jokes are funniest. PJ gives the example about the one where Helen Keller falls down a well and breaks three fingers calling for help.
The leftist, humorist or not, looks at the world and sees what needs changing. Look at how many politicians 'go into politics to change the world.' The rest of us can see what's funny, and laugh about it.
By the way, what do Charles Kennedy and Mark Oaten have in common?
They both like to get shit-faced. And there's nothing funny about that.