Yes, the moderator's behaviour would have been wrong against any person, no matter their gender. But it is especially inappropriate when done against those who have to endure this more than others throughout their life.

You don't need a sexist intent to behave sexist. Being ignorant to this issue doesn't make it much better. And calling the person from the audience "heckling" just because she made him aware of this issue is a very clear sign of ignorance.

At least he changed his behaviour nevertheless, although I'd attribute this more to the reaction of the rest of the audience.