Who's obsessed? It's a joke about a dude attempting to man-splain even when they're wrong (I'm a dude and I've definitely seen it) and her turning the tables on him. That's it. To get defensive about that is... weird.
Mansplaining (a blend word of man and the informal form splaining of the gerund explaining) is a pejorative term meaning "(for a man) to comment on or explain something, to a woman, in a condescending, overconfident, and often inaccurate or oversimplified manner"
It's not meant to be a stereotype applied to all men, just the a thing that some men do. It happens when a man assumes, perhaps subconsciously, that the woman he is speaking to is his intellectual inferior and would surely benefit from his opinion on whatever topic without any regard to her possible expertise on the topic, or even his own lack thereof. I've rarely witnessed it myself, but know women who have had to put up with it. Stereotypeing all men as "manslainers" would be rude, but mocking the men who actually behave that way is cool with me.
Even the term itself is a generalising stereotype. But it we are to have a somewhat serious discussion about it, I'd say It's a human condition, not a gendered condition. For example, given what is (not) known about our respective genders, you felt the need to explain this.
What are you talking about? I've witnessed it several times now at work, especially regarding programming or EE. Have you not yet suffered through a programmer condescendingly explain trivial matters to others, especially to women?
The post is obviously a hyperbole but it's not too far off from reality.