the listener listens

You don't have to be a jerk about it. The most effective yet civil way of dealing with harmful "humor" is just pretending you don't get the joke and asking them to explain. "I don't get it, what's girl math? What's a girl dinner? What do you mean by you're just a girl? Can you explain the joke to me?"

It really does feel like we've done a massive backsliding in gender stereotyping over the past few years and it's honestly alarming.

Not just the "girl x / boy x" like "girl math" to mean being stupid and bad at math, or these "lol girl dinner" posts where it's a can of energy drink and half a jar of olives.

You know human sexism is out of hand when we have to project "boys are silly lovable goofballs, but girls are cold and mean" onto animals who have no concept of and absolutely do not adhere to human gender roles and stereotypes.

The sad thing is that this has real world consequences for these animals. On average, male cats and kittens have shorter stays at shelters due to being adopted quicker than female cats and kittens. I have no concrete proof that this is due to stereotypes of boy cats as lovable goofballs but girl cats as cold and mean, but my own lived experience is that I know several people who have prioritized adopting male cats and kittens due to this (incorrect and sexist) assumption.

Of course cats all have different personalities, if you've ever had cats you know this. But it has no basis in gender roles or stereotypes. I've had boy cats who were aloof and unfriendly, and I've had girl cats who were sweet little cuddlebugs with everyone they met.

She stopped because I wasn't laughing. (Also he turned out to have a heart condition so it was good that I told her to get him to the hospital)

(Edit: sorry didn't finish my thought)

Like there's so many "jokes" that just aren't funny once you need to explain them. It really makes people think a bit harder. Like old coworker saying "my husband is an idiot, he keeps falling asleep on his tractor" or "my husband is an idiot he fell asleep in his chair and spilled his beer"

Although that's not to say that weaponized incompetence is the culprit every time. For example, in my family and among my in-laws there are plenty of men who genuinely want to do more of the cooking and/or baking for family gatherings, but their girlfriend or wife doesn't allow it because they want everything to be perfect, and think allowing a man in the kitchen will result in less than perfect food that doesn't wow the guests the way she wants. (Yes, even here in supposedly oh-so gender equal Iceland people get weird and sexist about things like this)