I’m sorry, golfer – now that I think about it, the assumption was likely three-fold:
1) A simple assumption that most girls wouldn’t degrade themselves like that.
2) I tend to think of sarcasm as more of a male tendency, which may be based on an ingrained chauvinistic view (that I’m not proud of) that all women are dainty creatures who wouldn’t dare say something that isn’t proper and polite.
3) As a guy, if I don’t think about it too hard, I automatically assume everyone else on the internet is a guy.