Its not that i'm against the idea of you to protect your son and their buddies, it just seams like complete common sence to me.
It's a sharp metal spinning disk, you shouldnt put your fingers anywhere near it.
Are you going to put Carbon Fibre protectors near any sharp objects that your kids and their friends have access to?
Are you going to wrap them in bubble wrap for the rest of their lives, rarther than explain to them the risks of life?
I don't question your reasoning behind protecting your kids, i just simply think there's better ways of doing it. You should be teaching them to fend for them selves, to teach them to see the dangers in life for them self, rather than you protect them,