Of course employees should be able to voice concerns about projects and policies and suggest an alternate strategy. But if leadership rejects that alternative strategy, that needs to be the end of it. If leadership disagrees with you, you can't just start leaking stuff to the press, doxxing people, and organizing protest events. A company is not Twitter and any healthy company should fire employees who are confused about the difference.
Not infrequently the consequences are literally disastrous and/or fatal. (See also Boeing, Lehman, Enron. HP at its worst, and many many more.)
What exactly gives corporations the moral authority to act like this?
Is it simply that large accumulations of money somehow render other moral concerns irrelevant, as if by magic?
I mean, maybe. They'd ban them if the few people were the owners and the SVPs.
If they company did, they'd be within their rights to. The only problem would be all the money they'd leave on the table. Usually (1), that's been the backstop against corporations operating with their private ethics on their sleeve; corps that make a habit of leaving money on the table tend to get left behind by the market.
If Google started banning GCP use for ethical reasons, some other company would step up to fill the gap; no doubt.
(1) Usually. Chik-fil-A supports conversion therapy for LGBTQ people and Hobby Lobby's owners have used their assets for "art acquisition" that was illegal.