Claude Puel insisted referee Lee Probert was correct to book Demarai Gray for his shirt-off goal celebration in tribute to the late Leicester owner Vichai Srivaddhanaprabha.
Gray struck a 55th-minute winner on an emotional afternoon in Cardiff and marked it by removing his top and revealing an undershirt with the words 'For Khun Vichai' on it.
Thai businessman Srivaddhanaprabha and four others were killed in a helicopter crash outside the King Power Stadium last weekend.
Gray's booking under disciplinary protocol provoked a fierce debate on social media, with many fans believing Probert should have ignored the letter of the law and not brandished a yellow card given the highly-charged circumstances.
Leicester fan and Match of the Day presenter Gary Lineker, on his Twitter account, called it a "silly law, always has been but not the day to get worked up about something so insignificant."
But Leicester manager Puel said: "We played like professionals and it was important for the referee to be professional too.
"He knows the rules and it was important for Demi to take this yellow card.
"It was the one time I accepted a yellow card from my player. It was very emotional."
Leicester's players wore t-shirts during the pre-match warm-up bearing an image of Srivaddhanaprabha's face and the words 'The Boss', the title he was known by at the King Power Stadium.
Fans wore identical t-shirts in the away end, and the entire Leicester playing squad and backroom staff lined up around the centre circle for a minute's silence before kick-off.
Both sets of supporters unfurled giant banners in tribute to Srivaddhanaprabha, and it was clear how much Gray's goal and the victory at the final whistle meant to Leicester.
"It was great to experience this result with the fans at the end because it was all the family together to honour our chairman," Puel said before he and the players embarked on a 13-hour flight to Bangkok to attend Srivaddhanaprabha's funeral.
"It was tough all week. We went step by step, we came back for training and worked together.
"We saw all the tributes before the game, we share a lot of feelings and it's important to continue the work and keep finding the right balance.
Cardiff fell into the bottom three as Newcastle climbed above them with a first win of the season.
"It's been a strange week, surreal really, and I'm glad it's out of the way if I'm honest," manager Neil Warnock said.
"The players gave everything but it's been difficult this week, three or four lads in particular.
"Whether it's triggered things up I don't know. But training's not been the same and we had to have a word with them that we've got to play the game."
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