I think you'd want to give Facebook employees an out, such as asking them to speak to a better vision for Facebook. Or ask them to tell you that respecting a user's privacy and not manipulating their emotions is paramount at your company.

But the real intention of such a policy isn't to protect Facebook employees or make them feel safe. It's to make potential future Facebook employees think twice about seeking work there. Get them to question the things they would have to do or overlook if they chose Facebook instead of their other options.

Eventually such a policy might cause the Facebook's workforce to hollow out.

Society tells people that stealing and murder are wrong, and we point to the moral and judicial consequences of these actions. I don't see why similar social and career consequences for working at Facebook wouldn't help. And as you brought up, I think it's appropriate to give Facebook employees incredible latitude to side-step such a hiring ban. The goal isn't to harm the employees so much as it is to protect your own company's culture and to hopefully decrease the attractiveness of working at Facebook.