Right, in a perfect world of responsible people. However, we are very far from that world. The determination should be: If saying people can unmask when fully vaccinated leads to increased vaccinations that outweigh the added infections from unmasked people....then we should say fully vaccinated people can unmask. It isn't about what, in theory, should reduce spread/infection. It should be what, in real world practice, will actually lead to the least amount of spread/infection. Now will that actually lead to more vaccinations that outweigh increased infections from lack of masks? I would probably lean towards no because of the massive increase of non vaccinated people now unmasking because no one will ask them if they have actually been vaccinated. I agree with all of this, save for the fact that your equation has to also account for the fact that many of those now unmasked, unvaccinated people were already unmasked in most situations.