JUSTIN BIEBER VS KEYSHAWN - "Where you running to, White Boy?"

Few days ago, Keyshawn Johnson chased down a speeding Justin Bieber and tried to confront the him about his dangerous driving habits -- but Bieber ran away like a scaredy pussycat..  

Keyshawn is a former NFL superstar.. He had just left a party Sunday night inside of his exclusive gated community in Calabasas (with his child in the car), when Bieber zoomed by in his Ferrari, speeding like an F1 racer. 

Keyshawn was so pissed, feeling Bieber could've killed someone -- so he dropped his kid home, then chased after the Bieber in his Prius (Prius - Tiny car). 

When  Keyshawn got to Bieber's crib, he blocked JB's Ferrari in the driveway and got out of his car to confront Justin face to face, but Justin ran inside his crib like a wuse and refused to come out. 

FYI -- Keyshawn is 6'4", 212 lbs ...  Bieber's about 5'7", 110 lbs. 

At least 2 people called the police on Justin that night, and cops visited his cribs.

Sources say Several people witnessed the speeding incident, and say Justin was definitely in the driver's seat... Also the witnesses told Sheriff's deputies: "Bieber appeared stoned at the time"