Karl Robinson says the furore around Dele Alli's middle-finger gesture has spiralled out of control and should be forgotten.
Alli caused controversy during England's 2-1 victory over Slovakia on Monday when he was spotted making the signal at Wembley.
Referee Clement Turpin was initially thought to be the intended target, but the Tottenham midfielder and England boss Gareth Southgate insisted it was a joke with team-mate Kyle Walker.
Jamie Vardy labelled the incident as "harmless banter" on Wednesday, and Robinson has also come out in defence of the 21-year-old, to whom he gave a league debut while at MK Dons.
"I'm sick of people having a go at him. Just leave him alone," Robinson, now Charlton Athletic boss, told a media conference.
"The kid just wants to play football. What he did probably wasn't right, but he sees that football pitch as how he saw his old school playground. That's how he plays. He plays free. That's how he plays.
"It's typical of us, though, isn't it. He's made one or two little mistakes and everybody in the country is looking to nail him to the mast.
"He's done what he has done and he'll learn his lesson. I will always back him."