"but perhaps boys and girls are different" should be interpreted as a joke; specifically satire on people who actively push that there are no differences between the sexes.

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To bring some context:

I have a friend who called up other friends in the group and repeats over and over that there's no difference between the sexes, that it's artificial, ect. He did this when he dated a trans woman, yet didn't seem to realize that his partner felt so strongly about their gender that they changed it.