Boss messages employee at 8 PM, laughs when employee says their contract says 9-5: 'You disregarded your own boundaries by replying to him'

Would you answer a work text outside of your regular working hours?

This probably depends on what your job is and how much you're invested in it. If you have an insane job that requires a lot out of you, you might be used to dropping what you're doing and attending to your job. But it's also important to have boundaries with your personal life. You have to know when not to answer the phone. It's not always your responsibility to be available all the time. Unless it's a life-threatening situation, which it rarely is, you should be able to clock out when you need to clock out. 

Part of this boundary-setting is on your employer. They should know not to expect a response when their employees are off the clock. It's an overreaching of power and an invasion of privacy, but not all bosses understand that. A key part of protecting your peace is realizing that you cannot control the actions of others. You can only control your response to it. But this is much easier said than done. Sometimes you wish you could just make someone do what you'd like them to do. But this is not how the world works, and we're obviously better off that way. So what we're left with is just to manage our own expectations and the expectations of those around us. That's what this employee failed to do, and he paid the price for it. It's not an easy thing to do in the workplace, and he wasn't totally up to the challenge.