so what would have happened if he went through with a scarf round his head then ? hope he found out after all that hassle
Probably nothing... Other than a few odd looks.
You would and should be asked to remove it, the same as outside coats, gloves etc. If he had a scarf around his head 100% he would have been asked to remove it, the same as if it had been round his neck.
Try it next time you fly.