How to express sexism through punctuation

There is an interesting question that is used to show people their own biases that is pretty interesting. I've used it before and I've gotten tons of answers that is supposed to show you have I bias against thinking women can be doctors or even homosexuals can be doctors. I may butcher it but here it goes. (Mind you I kind of ruined the point of the question by telling you it's purpose beforehand)

A child and his father are brought to the hospital after being in a serious car accident. The father is unfortunately dead. The child has been stabilized but is in need of surgery and possible amputation. The surgeon walks into the room with the child and immediately turns around and goes to one of the nurses and says "I cannot operate on this child he is my son."

How does this statement make sense?

Interestingly out of the few dozen times I've asked this question while most people get extremely confused and immediately tell me that "you said the father died." The second most common answer is that the boys parents were a gay couple and the least common answer is that the surgeon was a woman.

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