Earlier quoted context omitted.
Why should employers have any control over your life whatsoever after they're not paying you?
their investment in teaching you their IP -- that's the theory you trade getting to learn for agreeing not to use it against them for a while -- is the theory at line worker level i'd argue this is nonsense, at 'how to mill iPhones from a single block of metal' or 'self driving car brain' maybe its real, but there are ndas and patents for that
To impose punitive measures after-the-fact because someone taught you how to do a job that they needed you to do seems hilarious even on the face of it.
To be clear, saying "You're not allowed to use our IP or our machinery or our supplies" is totally reasonable; if I quit Starbucks, then of course I won't have Starbucks machines or merch. To say that you're not allowed to do something because they happened to be the ones to train you seems just silly.
I get very strong middle-school vibes, where you introduce your friend-from-another-school to your group, then get mad when they become better friends with someone else than they are with you.