moot point as people should not be forced to wear them anyway. Whether they are actually harmful would be a non-issue as why would people go to the expense and bother of purchasing and wearing them, unless they were criminals & just wanted an excuse to hide their faces.
The author linked to a study on the CDC site itself indicating that there was no substantial benefit that could be found for wearing masks.
https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article
Given that, the author claims > 800 citations in his book of professionals expressing concerns over damage, especially to children from wearing masks. He also mentions at least one of the (CDC?) studies that found that improper wearing of the masks actually increases the risk of infection... and that the majority of people, often including even health care professionals, do not wear them correctly all of the time, or perhaps any of the time.
I remember seeing a picture of a teacher taping a mask to a young student's face. That can't be good for the student on at least a couple of levels.
I have heard a psychologist on the radio saying that masks are bad especially for babies and very young kids, even if the baby isn't wearing the mask. Seeing the faces of people, especially parents is very important for the development of socialization in young children and having people's faces partially covered almost all of the time certainly has risks for them.
We see that the rates of depression and suicide have jumped dramatically because of covid and the fallout due to society's reaction to it. It makes sense to suspect that all of the mask wearing plays a role in that, no?