Really? Just how many idealistic engineers are there?
Sincere idealism is rare. Most of the engineers I've met just want to make lots of money and work on interesting stuff, which is likely why the overwhelming majority of Google employees are still working there.
Like you identified, the idealistic ones will protest and maybe quit. Google will still likely be okay, it just won't be the place where idealistic engineers flock.
Look at the ACLU: it still holds tremendous cultural cachet as the defender of free speech - but there's been a generational change, and while plenty of the old guard still believe in that ideal, there's a whole new guard that have basically the opposite stance - they're concerned mostly about stopping "Hate Speech". There's a really good argument to be made that they are right to do so, that they're trying to clean up the mess that their predecessors made.
(But I don't buy that last argument in the least, personally)