I think the author understands that "have a little empathy" is a request to modify their behavior, but expresses their frustration that the request is unclear and (in the author's experience) the requestors won't clarify the request.

Contrast this with the conversation we're having now where I requested clarification on your initial comment, and you thoughtfully provided it.

But to your point, there's an innate "getting it" where your level/expression of empathy is roughly in-line with people you interact with, and if you don't have that, you need to do work to "get it", which is what the author did.

We can compare empathy to other practices that can benefit from innate understanding. Some people "get" poetry, math, music, long-distance running, etc. and we can all work to "get" them, but in my experience, it's never quite the same.