Just keep up the moral and psychological pressure, that's all it takes. Look at the constant leftward drift in academia. Not all of that is rich donors mysteriously interested in political agendas that involve increasing their own tax rate; most of it isn't.
The sort of people who would politically oppose them are conservatives, who by their very nature tend to be ... conservative. That is, careful about challenging the status quo and uninterested in activism. So frequently they just stay quiet and don't talk much about their views: that's why the walkouts and Googler activists on Twitter always seem to have the same agenda. It looks like Googlers all agree but they don't, not at all.
But this has an insidious impact in two forms:
1. People whose own convictions aren't that strong can be easily swayed by constant arguments of the form, "if you disagree with me you're evil and bad" because everyone wants to be good and they're not being supplied with intellectual ammo with which to fight back.
2. People who are trying to calculate the cost of resistance look around and don't see any allies, just a big angry mob, so feel they have to fold even if they disagree.
The correct way to handle this sort of situation is for senior managers to have strong and relatively small-c conservative convictions, such that progressive placard-waving activism is swiftly dealt with via firings with everyone being made clear on why those people got fired (political arguments do not belong in the workplace).
Google doesn't have that and we can see the result.
