First off, I don’t like Mr. Williamson’s characterization of people who don’t like this as “rabble”. Keep in mind National Review also thinks John Derbyshire is rabble, too.
Secondly, one of the reasons for not allowing facial hair is not just for practical reasons, but to make everyone as close to being the same as possible. That’s why there are regulations for hair and uniforms. Yes, someone with dreadlocks or a punk-rock mohawk can fire a gun. You want everybody to look like a unified force.
Can you imagine an officer with a beard inspecting troops, and telling a soldier with some beard stubble that he’s a mess, and needs to shave?
If having a beard is ok, then anyone should be allowed to have one no matter their religious beliefs.
What’s next, female Muslim soldiers with Burkas?