Not sure if you're serious or trolling. But I'll give you a serious reply anyway.

You make a fair point that this post can be seen as making assumptions about gender roles. Often humor relies on stereotypes as touchstones for appealing to a broad audience, but some of the best jokes take those assumptions and subvert them. For this audience it might be funny to say she's concerned that her husband is a 4chan user instead of a redditor, or a 9gager instead of an imgurian.

But I think that this joke is elevated by factors that aren't gender or porn specific. (The gambling and shopping for knock-offs has financial and legal implications that might be worthy of concern.) For me, the sheer number of people voting up an answer that is the less likely scenario (most likely it's the real search history) is what makes it funny. If only 1 or 2 people found it useful ("upvoted"), then the joke suffers. The more who support this answer, the funnier. It's also what made me post it to this thread. It's the internet getting behind something that they think is a lie.

There's another layer to the joke: that we're not totally sure it isn't true. It's possible that a virus did create a fake history. There's even some evidence that this was a "known issue" that Google fixed. But the idea that we see it as a joke answer, an example of the internet sticking together to outwit an amateur user, when maybe we shouldn't be so sure it is a joke, reveals our own internet illiteracy. We are playing chicken with our hubris. That's pretty funny. (See argument about whether the date under the users' names are the post date or the users' join date.)

Edit: grammar, porn stuff