There is nothing to hate here. I have given numerous PIP's as a manager and only actually fired once. The purpose of a PIP is to improve, not to fire a person.
How on earth can you be a good manager and not realize that saying "your performance is shit, we're going to fire you unless you take this course and we deem you've passed" is totally and utterly soul destroying to a person?
There are a million examples of why they are bad, and I can’t really think of any in which they are useful on their own. Which becomes the issue when decision makers advance in ranks and “I don’t dare make decisions without covering my ass” managers slip in. Or when HR gets too much political power and push their tools as the law. Often organisations simply grow into poor cultures because the systemic value of measurements is shit compared to individual management. This is of course helped along by bad managers, who when given too much freedom create an organisational culture which is far worse than the meritocracy of data driven management.
I think it’s a little rough to judge someone who may have grown up in these cultures as a bad manager from a couple of lines of text.