My belief re: the no masks in school under any circumstances thing is that there is a certain degree of magical thinking at work. Yes there are lots of very determined people who have very definite reasons why it is an awful idea and can't be considered and they will tell you all of them, from every angle and it doesn't matter that all the reasons are coming from disparate approaches and have spurious evidence behind them because they feel very real to the people giving them.
But I think it boils down to a degree of (often completely unacknowledged) fear.
Sending a child to school in a mask means acknowledging that there is some sort of risk involved (because you have taken some form of mitigating action, hence there must be a risk to mitigate) this means that the child has a chance of coming to harm and that is something that so many of us can't cope with. The thought of knowingly putting our child in harm's way is awful, to all of us.
So if we refuse to even consider a mask we resist the idea that harm can come to our child, there is no need for mitigation because there is no risk. No danger. Everything is fine. Just as it has always been. There's no need to grapple with the difficult decision of whether their education or their health is more important, there's no need to think about impact on the wider world, because there isn't a problem to start off with.
Those who admit the risk and take steps to reduce potential harm are poking at that very fragile bubble of denial and are lashed out against, because they are threatening a very deeply held coping strategy.
That's what I believe anyway. And if people are allowed to believe whatever they want about the nature of viral transmission despite having no actual in-depth knowledge of the topic then I am allowed to believe whatever I want about their motivations.