Reader: Inspired by your advice, I've made a number of successful changes that involve actively denormalizing the [sexist] microaggressions and empowering others to do the same.
Second, I have made every response either (a) dispassionate: "Huh, I don't think most people really use 'girls' and 'boys' in the workplace anymore," or (b) as awkward as possible, with a head cocked in disbelief or an "okayyyyyy then, moving along," as if embarrassed for them. The former pushes them to think about what they said from a nondefensive place, and the second forces them to reflect on what part of what they said was awkward and inappropriate.
Third, I've been consistent in calling it out without exception: women, men, young, old, supervisors and clients. It's become as normal and casual to me as correcting name pronunciation.
In my environment, a simple "Ha! that's an old-fashioned line I don't hear much these days," or "Sounds great, Amy, but let's introduce our team as 'women' when we go in this time," has worked really well. By talking with female associates and clients about adjusting our own interactions, I see much better results than if I try to fix everyone's interactions with women. Call-out culture can be perceived as aggressive, and no one likes to be lectured.
Fourth, with male managers, I'm slowly bringing up the issue in shoptalk, the way I would share a budget concern or a rushed timeline. For instance, "Is your team holding up okay after [the supervisor] spent this morning's meeting calling them all 'girls?' " or "My project keeps stalling because of bad morale. Have you had any luck dealing with some of the sexism from [the client]?" If we're just talking business in a general sense, defenses are down and — as you advised — they have a chance to consider the effect from a bottom-line standpoint.
Finally, I had to file a formal sexual harassment report on a relatively new manager, which gave me an opportunity to discuss not only the specific incident with HR, but also the culture that fosters pervasive harassment and how hard it is to report. Because I presented the Bad Culture as a bottom-line issue and was able to speak to concrete instances, the HR manager was open to the rest of the data and the "theoreticals."
While I'm not sure what filtered up and out from this discussion with HR — aside from the perpetrator correcting his behavior — I have yet to be called "girl" again by anyone with the company!
Karla: Much as I’d like to accept the credit, you’re the one who turned suggestions into a customized strategy, diplomatically delivered. And now I have to walk back my earlier position and concede that it may be possible after all to both keep your job and “drag [your] company into 2019.”
Pro Tip: As this reader realized, “I” statements, particularly “I feel” statements, are useful in softening personal arguments, but can undermine professional ones. See an October 2018 Harvard Business Review article by management consultant Liz Kislik