I don't disagree with your rationale. I once saw the statement that in order for a company to succeed, they either have to figure out how to hire well or how to fire well. If you do one well enough, you don't have to worry as much about optimizing the other. Most companies just prefer to focus more on hiring well because firing people is unpleasant.

And what about what’s best for the person being fired? Or are they just a cog in the machine, unworthy of empathy or decent treatment?

If someone can't perform the job, the only option is to let them go. As I said in my original post, it rarely happens because it's actually not that difficult to vet someone without forcing them to write tons of code.

In order of importance a manager should put the company first, then team, then individual employees, then themselves. Poor performers hurt everyone on that list.

If you hire someone who is currently employed and then fire them, you are doing very real damage to their finances and career. Empathy for employees is a valid reason to err on the side of avoiding bad hires over easy in/easy out.

I disagree. By optimizing to protect poor performers, you jeopardize all employees. It's more important that the company succeed and that people who are good at their job get to work unencumbered.

Framing the decision to fire someone as a trolley problem (cf. https://en.wikipedia.org/wiki/Trolley_problem) doesn't make you look any less cold-blooded :)

Have you ever been a manager? Again, it's not being cold blooded, it's one of the main responsibilities of the job. Being a leader isn't easy and you often have to make tough decisions and sacrifice in the name of the team. This has been well known throughout the history of leadership.

It shouldn't be looked at that way and it's not black and white. Ideally they're treated like people, not cogs, and the manager and company does what it can to either get the person the skills they need to succeed, move them to a role they can succeed in, or give them a path out in a reasonable amount of time.

Most of the time the under-performer will be happier after any of these scenarios than they would knowing they're under-performing in their current role. It just takes a bit of time and maturity to realize.