On another site that I frequent I was witness to an exchange.
One poster, long since admittedly 'female', upon finding out that another poster was a man stated the following:
"All those wonderful pictures (nature scenes) you have posted, I thought you were a woman all this time."
I told the poster she was being sexist in making a gender determination based only on the sort of content that someone posts.
That poster refused to even acknowledge my reverse analogies, such as, after dining at Sylvia's in Harlem, Bill O'Reilly stating surprise that black people weren't swearing every other word was very racist of him. He just laughed it off. The other poster took no offense, he was just gracious for what he chose to perceive as a compliment... much to his credit.
So was I wrong? Is it at all sexist to assume someone is of a particular gender just because their posts are of a certain character or content?