I'm always afraid to tell the person cutting my hair that I don't like what they're doing . . . they have a LOT of sharp objects around.  But here's a sharp object I never even thought of.

A 33-year-old guy was at a barbershop in Brooklyn, New York on Thursday afternoon, and he told his barber that he didn't like the haircut . . . and he even threatened not to pay for it.

And the barber responded by . . . throwing him THROUGH the front window of the shop.

The guy's face got messed up pretty badly by the glass and he was taken to the hospital in an ambulance.

The barber ran off, and the other people at the shop said they didn't know his name or how to reach him . . . so the cops are trying to track him down