About protective gear...

Everyone is wearing vests and helmets because normally that's pretty good protection in a fight. They didn't KNOW they would necessarily be getting shot in the face when they put it on.

The glass visors aren't designed to take a bullet, but they would protect from a knife or shrapnel or possibly a ricochet. Kevlar vests can't completely protect you from the impact of a bullet, but for those officers who got shot in the chest in the early police station scenes, it probably saved a couple of their lives. Plus kevlar isn't 100% effective anyway.

And of course, the reason they were getting shot so effectively despite the protection is that Jet Li is a beast in this movie.

Bullet proof vests(or helmets) are not actually bullet PROOF. And it still hurts like *beep* when you get shot even if the vest does stop the bullet.

Prof. Farnsworth: Oh. A lesson in not changing history from Mr. I'm-My-Own-Grandpa!