Another benefit that the face shield would add is that it would limit fights in the NHL.
I'll admit that I enjoy a good boxing match on ice here and there, but dropping your gloves and trying to punch someone's nose through the back of his skull during a hockey game is ridiculous. It just doesn't belong.
Every other sport has strict rules against fighting. After all, America's Funniest Home Videos would have appreciated Derek Harper vs. Jo-Jo English last year in the NBA playoffs. However, the league was completely embarrassed by the skirmish (which took place right in front of the commissioner), so the NBA cut down on fighting even more.
Hockey condones the garbage--five minutes in the penalty box for reducing someone to pulp? Heck, some guys use it as a good rest time.
Professional goons would have a harder time punching at metal bars or plastic shields. It would be tougher on their knuckles, and the league could easily eject anyone who willingly removes his helmet for fight-night.
If their knuckles give, then, well, they might have to find another job. Sorry, Tie Domi.
Hockey is a fast-paced sport, and the rushes of adrenaline can often cause people to lose their emotion and get into fight. But there is no excuse.
Likewise, the fast pace of the sport will cause many accidents. It's just that some of them can be avoided.
Mandatory face shields will kill two ugly birds with one stone.