Smash Mouth Singer Quit Tossing Bread at Us... You 'Punk Bitches'

6/15/2015 8:59 AM PDT

Smash Mouth Singer -- Quit Tossing Bread at Us ... You 'Punk Bitches' (VIDEO)

The lead singer of Smash Mouth lost his cool during a concert, and started cussing like CRAZY at the crowd ... all because of a little bread. 

The '90s band (still working the county fair & festival circuit) was performing at a Colorado food fest on Sunday when people in the crowd started throwing slices of bread on stage -- and when the dough hit lead singer Steve Harwell. ... he went off

Harwell lost his mind ... threatening to fight anyone -- at the family friendly event, mind you. 

Security stepped in though to block Harwell from attacking, and he returned to the stage to sing "All Star" ... which is all anyone cared about anyway.