The County defender was sent off after a VAR review for a studs-up lunge on Yang Hyun-jun.
Brendan Rodgers' Celtic also had two goals ruled out after VAR checks and were made to wait until the last action of the first half to take the lead.
David Turnbull took aim from well outside the area and arrowed his shot into the bottom corner for his fifth goal of the season.
Ahead of Tuesday's trip to Atletico Madrid in the Champions League, Rodgers made six changes.
But it was not until he made a triple celebration on the hour mark to bring on Kyogo Furuhashi, Luis Palma and James Forrest on the hour mark that Celtic cut loose.
Palma outdid Turnbull with another stunning strike from 30 yards that dipped into the top corner to make the points safe.
The Honduran then teed up Forrest for a simple header that ensured the winger has scored in 15 consecutive seasons for the Hoops.
"We made the changes because we wanted to keep the energy in the game and bring more quality and the guys coming on did really well," said Rodgers.
"Playing against 10 men is never easy but the players worked it out really well."
Celtic will end the weekend eight points clear as Rangers are in League Cup semi-final action against Hearts on Sunday.