Ball recently laid into Lakers coach Luke Walton ... saying he's "soft" and doesn't know how to properly coach his son, Lonzo Ball.

So, we hit up Byron to see how he would handle the situation if he was in Luke's shoes. Long story short, Byron says guys like LaVar need to shut their traps and let the coaches coach.

"Shut up. Stay put. Stay on the sidelines. We got this."

BTW, Scott's hosting a live music event in Hollywood Friday night ... that LaVar Ball will probably not be attending.