Ivory Coast international Sagbo had won the penalty that saw Hull score through Robbie Brady - a decision labelled "incredibly soft" by Canaries boss Chris Hughton - but minutes later was sent off after he clashed with Russell Martin.
It left Hull to play with 10 men for more than an hour but they held out for a deserved three points.
Bruce said: "The boy was silly - it was a rush of blood. He's done something stupid but we have got away with it today.
"I don't know whether it had anything to do with the penalty. It's one of them when they are both grappling with each and he has put his head there.
"He hasn't headbutted him but he has gone through the action and when you are 10 yards away from the referee you are going to be red-carded and rightly so. It was stupid."
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