> but are also expected to act as a reasonable person would for the good of the company

It's the people they represent, i.e. the shareholders, who get to decide what's the good of the company, and the board is simply meant to enact those wishes. This is a constitutional issue of representation: at what point do the elected representatives decide the current situation calls for a referendum instead of an ordinary (representative) vote ?

> The majority shareholder says jump off a cliff and we must obey” is nonsense

If the majority shareholder decides that, then 1) the board must resign at once and 2) any one minority shareholder must sue and have the Delaware Court of Chancery determine that the majority shareholder has abused his powers. I'm not sure what would follow that court decision.