"Yes, I am sorry that you have been told over the last year that masks don’t reduce oxygen, by emphatic and dogmatic people, but the fact remains that oxygen deficit during mask-wearing is very thoroughly established in peer-reviewed clinical data. Here, here and here, for example.
And yes, surgeons also suffer from deoxygenation. Excess of carbon dioxide, as it accumulates inside a mask, also is a mild poisoning of the entire body, and this is also established in clinical data.   So if you demand that a child, a worker, a traveler, a consumer or anyone else wear a mask, you have been demanding that they mildly poison themselves.
I know this is vexing for some to read, but you cannot inflict harm with any moral authority, and you need to stop that now that you know it’s a problem, if you want to be able to live with yourself, or to exist peacefully with a good conscience."