Relish in Chaos said:
I believe I've heard a couple of feminists and/or trans feminists who've seen something (as have I) in various media over the years that depicts men dressing up as women, or simply effeminate men, in a humorous light, and question why exactly that's funny. Why would the image of a flamboyant man or a man putting on a dress be so funny for the public, when no-one ever laughs when a woman decides to dress in feminine clothing? Does it potentially imply that society inherently sees femininty as inferior to masculinity, deeming it as trivial compared to the more typically unisex (as determined by society, of course) nature of men's clothing? Is the exaggerated nature of many of these drag queens' clothing and performances poking fun at the way women accessorise themselves, and/or is it an attack on the cosmetics industry? Is it simply because it's "not normal", so it's alright to laugh at people for not conforming to cultural normality?
If you're looking to understand the psychology behind why (some) people find drag amusing, then I think you perhaps need to step back from any social commentary, and first work out what the fundamental question being asked is.
In this case, it's not anything to do with gender, or even necessarily culture, at all. Gender/culture roles and perceptions is a misdirection you've set for yourself, because what you're *really* looking to analyse... is comedy

, the far more fundamental/abstracted question of 'what makes something 'funny''.
Rowan atkinson did a neat video on the subject.... sorry for the subtitles but i was lazy and just went to the first video of 'laughing matters' i found. I did however link you directly to the part in question:
https://www.youtube.com/watch?v=E9fsn6lQBV4&feature=player_detailpage#t=321s
((at 5:20 if you're not following the link))
There may also be social or gender considerations that play their part, but it ultimately comes down to the unexpected being amusing, which is a pretty interesting insight(atleast, to me it was). For people who do not find drag to be unexpected, or have become accustomed to it, the amusement won't be there, because that's just how our brains work. Same reason why hearing the same joke over and over becomes less funny, it's no longer unexpected.
My question has always been on the next level down though... why are unexpected things amusing? I kinda have a theory that in the same way some mental illnesses include abnormal responses to certain stimulus, laughing at unexpected things is our brains not knowing how the hell to respond and so it goes with amusement. Amusement in turn may have then lead us to seek out more of these unknown/unexpected things(since it makes us feel good/happy), and thus this 'abnormal' response helped us evolve and learn and thus survive, becoming the norm in our species.