Managers rejects employee's 2 week's notice, tells them 2 weeks starts after they hire a replacement: 'That's how someone tries to squeeze free labor out of you while shopping for your replacement'

That's simply not how it works, boss. 

A two-week notice is a courtesy. It's what you do if you're trying to leave on good terms and you have a little bit of time to spare. It should give everyone enough time to get their ducks in a row before you go on your merry way. It's not a necessary thing. It's what you do to be nice. That said, we should do our best to give it when we can. After all, you've probably made yourself invaluable, and they might be scrambling to find a new you. But under no circumstances can your boss reject your 2 weeks. After all, you're not an indentured servant. You're there of your own will, and they can't force you to show up when you don't want to. What are they going to do? Fire you? You are already leaving. 

But some folks get an inflated sense of power when they're in charge. The responsibility goes to their head, and they rule with an iron fist. You might have someone like this in your life. They have gotten a little too big for their britches and need to be reminded of the true stakes of things. Very few jobs are life and death, even if employers act as if they are. It's your job as an employee to remind everyone to take a breath and to recognize your boundaries as a worker. You get to be there on your own terms. They need you, after all.