Actually, I knew a guy who used to smuggle drugs into nightclubs in his afro, so targeting people on the basis of whether their hairstyle is physically capable of concealing contraband seems quite reasonable.
If you don't like it ... then you are free to change your hairstyle ...
Then given the sacredness/importance of human life, relative to the value of someone's hair, there is no reasonable justification for not requiring every airline passenger to shave their head before entering security, if it reduces the probability of the scanner having false negative even by a small margin.
Come to think of it, there's no justification for allowing passengers to keep their clothes on as they pass through security.
Perhaps we should submit travelers to regular cavity searches, because I know someone who would smuggle contraband (including phones) into jail through a certain orifice.
I will never discriminate against someone for something they can't reasonably change. But discriminating against them for something they consciously choose is totally fine in my opinion.
If you don't like it ... then you are free to change your hairstyle ...