Jose Mourinho insisted Ovidiu Hategan is a "very good referee" after PSG's match with Istanbul Basaksehir was suspended over an alleged racist remark made by Hategan's fourth official, Sebastian Coltescu.
Players from both sides walked off following the incident in a gesture Tottenham boss Mourinho described as "iconic".
Coltescu is accused of aiming a racist remark at Istanbul Basaksehir assistant coach Pierre Webo - who was shown a red card in the 14th minute - before players from both sides left the pitch.
UEFA are investigating the incident and the game is set to be resumed on Wednesday night with a new set of officials.
Mourinho described Coltescu's actions as "unacceptable" and said he must "accept the consequences" as he expressed sympathy for Hategan.
"It's a very sad situation and every form of racism has to be fought. It's never accepted. I'm very sad because we don't want that in football," said the Spurs boss.
"I personally know the referee, Ovidiu Hategan. Good guy, very good referee. To be involved indirectly in a game that will become quite iconic is not a nice thing.
"The fourth official, only he can express his feelings. Of course he made an unacceptable mistake but only he can open his heart, apologise and accept the consequences. Probably he is a very good referee.
"Everyone in football and society, we have our responsibilities in relation to these situations and if we make mistakes, we have to accept the responsibilities.
"But more important for me is that that game becomes quite iconic. Champions League, to stop after 15 minutes for a very sad reason, will become iconic and hopefully, in the future, never happens again.
"But as a football guy, I'm very, very sorry that in my industry, that situation happened."
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