He appealed to people to remember Mr Sherriff and "walk away" if tensions build up at a bar.
Charles took a beer bottle from Mr Sherriff's hand and swung it behind him, where it broke, and then plunged it into Mr Sherriff's neck.
"It was a lethal weapon. He was a decent man," the judge added.
He said Charles had done something "which was truly out of character".
Andrew Hall QC, for Charles, said he acted "in a split second of madness".
Graphic designer Ashley Charles has been jailed for a minimum 14 years at the Old Bailey after being convicted of murdering telephone executive Phillip Sherriff after a Jessie J gig in London.
Ashley Charles has been found guilty of murdering Preston father of two Phillip Sherriff at a nightclub in London.
Mr Sherriff, 37, died after being slashed in the neck by a broken beer bottle.
He had been at the bar of the Pulse nightclub in central London when there was jostling by Charles.
Charles, a creative director, sat in the dock and watched CCTV footage of the attack. Mr Sherriff's widow wept a few feet away at the back of the court.
The trial was adjourned to tomorrow.