That's not even the OPs argument, nor is it some "ole" argument. You have both put words in their mouth and framed it as some classic well-known fallacy of which it is not.
The OP is making the distinction between "voting with your feet" which takes real commitment and has immediate effects versus "signing a letter"[1] which involves nothing more than a few seconds of your time without having to leave your desk.
If Google has trouble attracting talent due to matters of conscience it directly impacts its abilities to build new services as well as improve existing service in order to increase revenue.
[1] https://www.nytimes.com/2018/04/04/technology/google-letter-...
