Ok, my two cents (which in this financial crisis are probably especially worthless but even so):
First of all; Christopher Hitchens. Christopher Hitchens! For Christ's sake, what is the man if not a walking reputation of arrogance, boorishness and absurdity, the typical middle class white male, who fills his turgid waistcoats with ever changing opinions and a vast vat of self-importance. And this is to say nothing of his friendships with the odious Martin Amis and the ubiquitious God-bore Richard Dawkins (of which I admit his opinions should not be judged, although they do say one is judged by the company one keeps. Although I tend to think that one does not keep company, - as in chains and fetters - so much as inhabit it, unless they are Josef Fritzl and locking their company in a cellar). He is the definition of a prig. The one positive the man seems to have is the fact he can drink anybody under the table, including the table. First thing in assessing a piece of writing is the source, and Christoper Hitchens is like putting tomato ketchup on everything.
His article is ok. And does a bit of weighing and balancing but at the end he, inevitably, settles on stereotype and gender slander. I think the starkest undermining of the sanity of his opinion is when he professes Ellen DeGeneres to be funny. DeGeneres seems to me to be a HDD Converse wearing kid who tries to butt in on everything her guests say in the hope that she can espouse some genius one liner which usually falls flatter than a new residential development.
Ok, so women are sometimes considered to be unfunny, I can think of a few reasons for the prevalence of this opinion:
1. Old fashioned sexism, putting the woman in the corner. But this is not specific to humour, eg. woman are crap at DIY and driving etc etc. Women can't work or engage in politics. Women are crazy and emotionally all over the place - how did Hitchens put it? "Ruled by the moon and the tides". Therefore, women are incapable of almost anything. Some of these stereotypes might be based in some modicum of truth. For instance, as with porn, women have been proven to respond to more intellectual humour, that is to say humour with a storyline, characters, more wordplay and language involvement. As with porn, men tend to be about the physical and the action. A guy walks into a lamppost - funny. I guess the assumption is that women, instead of laughing, would rush to see that he wasn't hurt. Again, this is generalisation. A lot of men are much more into 'intellectual humour' and women into watching a man fall down the stairs, it's just that scientists and academics like to divide the sexes into neat columns of preference, and they have decided, apparently, that women prefer the witty one liner and men the gurning and gyrating of the performer.
2. On a professional level, there are more male comedians than women. Therefore the success rate, in this case "funniness" of the male comedians is most likely to be higher than that of the women comedians, as there are more of them and therefore at least some of them are likely to be really good. Why are the Russians and the Americans so good at sport? Because they have more people to choose potential athletes from. Why less women are professional comedians is a different question and not the same as why women are not as funny as men. My guess is that historically, stand up shows are linked to clubs and pubs and alcohol and this has always been more of a man's domain than a woman's, and some women wannabe performers will feel intimidated by this. And it's not just that women didn't do comedy in the past, it's that women did feck all in the past. By which I mean society prevented them doing so. As we have more businesswomen and more female engineers, we will have more comediennes, there is bound to be a lag considering past societal gender hierachies. And when the number of women comedians is equal, more or less, to that of men, then I am sure there will a similar number of "good" ones. At the moment, there are less to choose from.
3. In relation to the above point, it may be that there are less stand up circuit female comedians, but a lot of the funny women are engaged in other professions. TV, writing, acting, radio etc. Green Wing - written and produced by Victoria Pile, the same woman who wrote and produced Smack the Pony. Gavin and Stacey, co-written by Ruth Jones, Spaced co-written by Jessica Hynes etc.
4. As mentioned, in the past, men might have sought to 'woo' a woman with humour and charm. Although I can't see why a woman wouldn't choose to employ the same tactics to snare a man. I suppose being attracted to a man by a razor sharp one liner is the same as snagging your tights on a barbed wire fence. Well you're caught then. And maybe it is back to cavemen and men pounding their fists on their chests and doing a song and dance and women with hair that looks backcombed beyond mercy. But I think more and more confident women are expressing their humour and intelligence (and I would agree that the two are linked). The more society becomes at ease with strong, confident, intelligent women, the more that humour shines through.
5. Some men are stupid. Some men are sexist, some men are boorish and appreciate a particular type of humour which comes boxed with balls. These types of men will never appreciate 'female' humour - because they don't want to -even if the only thing female about it is that it comes from the mouth of a woman. (And not even a mouth necessarily framed with lipstick).
6. Some women are stupid. Some women are bitchy and jealous and mean. These types of women will never appreciate the success and talent of their 'competitors', and will only be happy when all other women are fatter/uglier/less sexy than them.
7. Similar to the above, because of ingrained cultural and gender relevant stereotypes or prejudices, it is, in some quarters of society, deemed 'unattractive' for women to be funny. Perhaps that is to do with the fact that humour is indicative of intelligence and men are intimidated by intelligence. Perhaps it is because humour suggests a loudness or brashness or level of confidence to pull off that is viewed as masculine. Perhaps it is because men feel it is a reserve of the male to be funny and intelligent and for the woman to swoon and flutter her eyelashes at strobe-lighting speed. I guess it's from the same stable as thought as the dumb and dumber antics of The Simple Life (although I actually think Nicole Richie has a wit on her that could give anyone a paper cut).
And of course the counter argument to all this is that, actually, there is a rich tradition of humour from women. Think of all the cabaret artists in the past. Ok, so again it was embroiled in the pleasing of men, the cheeky winks, the can-can of ankles (eg. Marlene Dietrich did cabaret during the 1960s I think), but women have, actually, been performing and making people laugh for some time. And I'm pretty sure there were some good female comedians during the wars, keeping things humourous.
And now of course we have a rich tradition of funny women, whether that be in stand up, acting, writing, radio, presenting etc. Joan Rivers, Shazia Mirza, Sandra Bernhard, Meera Syal, Sarah Silverman, Josie Long, Lucy Porter, Tasmin Greig, Jo Brand, the late Linda Smith, Jessica Hynes, Jennifer Saunders, Dawn French, Anna Faris etc.
I think there is also misconceptions and prejudices about material, "oh women only make jokes about periods" etc. Well, no, they don't, but even if they did, so what?! They're not allowed to make jokes about periods? And men aren't allowed to make jokes about tanking? I guess the problem is a lot of the response to humour - what makes things funny for us - is recognition, that feeling of "Oh, I so know what he/she means", and, if we go with the idea that most comedy audiences are male, then they are not going to get that recognition of knowledge from a woman talking about super plus tampons. But, did a little imagination hurt anyone? Joan Rivers makes glorious vagina jokes, just as Richard Pryor used to make great sex jokes about shagging women.
Ok, so it is ingrained from the past, but things change. These generalisations are absurd and, at worst, sexist and derogatory and at best, extremely intellecutally limited. Saying women are not funny, on a personal, situational level is the same as saying women cannot put up shelves, and saying women are not funny in a professional sense is the same as saying women do not make good engineers. Men and women are different, their observations and experiences are different, not better or worse, but different. And there will always be change and evolution within gender patterns and types.
I think, mainly, the only men who say "women aren't funny", or indeed women, who say "women aren't funny" are saying more about themselves than the effectiveness of female humour.