Why, you ask?

The band apparently took MAJOR offense to an interview Garrett gave ripping Kevin Durant ... where the Browns star said, "KD broke the league" by jumping to the Warriors to win a title.

"You hopped onto a 73-9 team and he took the easy way out in my mind," Garrett said on 92.3 The Fan.

He added one more shot -- "Me, I'm too competitive to try and ride on somebody's coattails to get a W."

Enter Smash Mouth -- big Golden State Warriors fans -- with expletive-laden Durant defense.

"Hey Myles Garrett,.....nobody knows who the F you are so nobody gives a F what you would do."

"And Genius the @warriors didn't win the Championship the season before KD signed. So not sure what 'coattails' you're referring to. This your Twitter page Aaaaahole? @MylesLGarrett."

So, what now? There's only one solution -- Smash Mouth must fight Myles Garrett.