I disagree because it's not even just about grants. At least in Europe most researchers are government employees so I don't care if your grant money is private,

I disagree because it's not even just about grants. At least in Europe most researchers are government employees so I don't care if your grant money is private, open access is still a basic requirement. If you want to publish research that requires me to pay 30$ an article to access you better not be doing that from a publicly funded job.