Can't you take a joke?

It seems a popular response to feminist critique, online and off, is "Can't you take a joke?"  Try it:  question how gender plays into someone's statements.  Nine times out of 10, instead of kicking off a discussion of whether or not your criticism holds up, you'll get dismissed as someone who has no sense of humor.

Two examples:

• Someone tells me to lighten up when I questioned an analogy involving programming and women's shoes.
• Someone calls me a humorless lesbian for questioning whether or not comments were homophobic.

My question is:  can't you people take critique?