Scott McTominay reportedly burst into laughter after a Manchester United supporter shouted "f*** Liverpool " during a kit launch in Melbourne earlier this month.
The incident happened during United's successful pre-season tour of Thailand and Australia. The Red Devils recorded comfortable victories against Liverpool, Melbourne Victory and Crystal Palace, although Steven Gerrard's Aston Villa held them to a 2-2 draw.
United have two more friendlies against Atletico Madrid in Norway and Rayo Vallecano at Old Trafford to come before their Premier League campaign gets underway.
Erik ten Hag's side will start the season at home to Graham Potter's Brighton on August 7. United launched their new away in Federation Square with the likes of McTominay, Bruno Fernandes, Jadon Sancho and Marcus Rashford in attendance.