To send a message, seems like. "Senior engineering lead fired for challenging corporate directive" might deter others who thought of taking a similar stance. "

To send a message, seems like. "Senior engineering lead fired for challenging corporate directive" might deter others who thought of taking a similar stance. "Senior engineering lead resigns in protest of corporate directive", on the other hand, seems like a call to arms for the conscience-driven; a thorn in corporate's side. Better to squash it and deal with the one-off "firing". Especially if it's for "cause"—then they can give nothing as severance, and quote a violation of the "employee agreement" as the reason.