alt Hacker News> It would be kind of hipocritical to act on your own morals using someone elses money - up to the point where it could be illegal misapropriation
This is hyperbole. Refusing to hire anyone out of any of the big tech companies is an own goal. But being silly in management is absolutely legal. The only legal obligation I can think of revolves around disclosure, i.e. you should be open with investors and the company about the fact that you're putting up these moral guardrails, rails which may have effects on the company's competitiveness.
It is not black/white. If you have a qualified candidate that asks less money and reject them over a less-qualified candidate on the sole grounds they worked for a prediction marked, it could be called silly. If the discprancy in qualification and salary demends is high enough and you do this repeatedly, it can be gross misconduct and not only a reason to be fired, but to be held financially liable for the damage.