I wasn't posting to you. Folks around here might know that I have a habit of chiming in on this particular subject, as I know I've done so many times in the past when it comes up. Sexism and other prejudices not consciously intended but nonetheless present are subjects I think are interesting. I'm posting about the topic, rather than discussing it with you. I take care to point that out not to be snarky, but only to be clear.
ElJay, it's interesting how sneaky the word 'girl' can be. Among men, being referred to as 'boy' can (outside the racial context, which is another thing entirely) often be considered a criticism. No word is the same for everyone, but in my experience the only time 'boy' will be viewed as a favorable word is when it's used in a clearly favorable way. "He's my boy," or variations thereof.
On the other hand, if someone said 'you pitch like a boy' to a 25 year old, chances are it won't be viewed as a compliment or anything but a remark on perceived incompetence. Whereas every single sporting reference to doing something 'like a girl' I can think of is clearly negative, unless it is coopted by actual female athletes. 'Hit like a girl', 'throw like a girl', 'run like a girl', all clearly bad. 'Women drivers', also bad. So on and so forth. In a culture so laden with gender-specific remarks of competence for men and incompetence for women, it seems obvious to me that if a woman hears an insult or criticism involving gender, she'll look to the conclusion that would be right in so many other cases, as of course it is in this one.
There's also another clear whiff here: that of the female as the giggling, whimsical, non-serious gender.