I'm not sure what you mean. All managers are paid to ensure better outcomes, where "better" is defined by the company (not by the engineers, except insofar as this enables the company's goals). Some managers are more effective at this, and some less. As a manager, sometimes it's better to have a cohesive team with consistent rules, even if some engineers will opt to work elsewhere as a result.

Although I am sympathetic with OP's feelings that a strict 9-5 rule is most likely unhelpful for everyone, I do think if the engineer took a confrontational tone, the manager would have no choice but to call his bluff. Any other move, and no one would take that manager seriously again. Therefore, the top answer in the original post is correct: ask nicely, and if compromise is impossible, start interviewing elsewhere. If he can really get a 40% bump, it's probably worth taking that.