You aren't mad at them, you're mad at the people making the decisions that are upstream of these meetings.
If my employer tells me to call a person and tell them they are fired because they did a bad job, but it's clear that this is not the reason, I would say: sorry, but I'm not going to do that. Remember, it's an "employer", not a "boss".
(But for what it's worth, this doesn't seem to me like a cut and dry description of what happened here; sales is a very cut-throat quota sensitive profession in my experience.)
But nevertheless, I empathize with people who also have to figure out how to put food on their own family's table, in a profession (HR) that is itself very sensitive to downturns.
The comments in this thread read to me like software developers who have not faced a world where it is not easy get a better new job easily after quitting one that sucks, and / or who are young and unattached with very few expenses, and struggle to put themselves in the shoes of someone for whom a principled resignation could have devastating consequences.
It just seems to me like a classic case of shooting the messenger.
In this case, it's not clear that this isn't the reason. That's something the laidoff employee calls out herself; the HR people aren't familiar with her KPIs or work. They don't have any expertise in her industry, and it's unreasonable to expect that.
Then they should not do that job.
People who work in HR do useful things. I have leaned on "people operations" support in most companies I've worked for, they do recruitment and policies on employee behavior and performance management and a bunch of other things. This is all valuable work. I'm glad it's not what I do for work, but it would be a much suckier world if nobody chose to do this work.
But they are also asked by company leadership to be the buffer, to be the messenger that gets "shot", when bad or even necessary but incredibly painful decisions are made. It's part of the expectations of the people who hire them, that they'll do that.
So what do you suggest? Do all the other useful stuff, but then when asked to be that buffer in these shitty moments, they should quit and find a new job? What should they say when asked why they quit? Is it ethical to lie about it, or do they tell a prospective new employer that there is an expected part of the role they're applying for that they are not willing to do?
Or is your suggestion something better? Like perhaps there could be a professional guild for HR professionals, and they could have a code of ethics that makes it clear that this is not something they will do. I think that would be pretty great! But that would be a much bigger and entirely different project that individuals quitting in protest.
Or perhaps your suggestion is, actually, that there should be nobody working in HR, that it is not a useful function. In that case, no, that's wrong, I've worked with many smart technically inclined people who think this, and I've worked at companies that are led by people who believe this, and it sucks.
I'm all for shifting the expectation of who has the responsibility for delivering the news of shitty decisions onto the management that made the decisions, but there has to be some theory of the case for how to get there from here.