Celtic were allowed to indulge themselves.
It must have felt as though the grievances left over from Tuesday's defeat by Juventus in the Champions League could be erased with every goal. The home side's ruthlessness was, in a sense, a measure of the discontent that had lingered. United became victims of Celtic's desire to make amends.
The home support pointedly cheered Efe Ambrose's first touch of the ball, after the defender was most culpable for the 3-0 loss to Juventus. He was also the subject of a sharp rebuke in the immediate aftermath by Kris Commons. Any air of discontent was quickly shattered, since the two players were prominent, but also clearly working in tandem.
It was from Commons' corner kick that Ambrose headed Celtic's equalising goal. The player was entitled to feel vindicated, even if his play was generally a mixture of confidence on the ball and momentary lapses of control. Nonetheless, there was mental strength in performing adeptly after the harrowing experience of Tuesday, and he received an ovation when he was substituted late in the game. Commons did so too soon after, and the players walked up the tunnel together.
"Ambrose and Commons were exceptional, in spite of all the talk beforehand," said Lennon. "It shows the dressing room is unified. It is no disgrace losing to Juventus. Some of the fallout after the game was typically over the top. The players would have been hurting, but they picked themselves up very well."
Celtic had to earn the right to stage manage the departures of Ambrose and Commons, who scored Celtic's second with a volley from Emilio Izaguirre's cross. The substitutions were designed to highlight their contributions, but also repair some goodwill. The same demands had been made of the team, since there was an early setback when Stuart Armstrong drove a low shot beyond Fraser Forster. The goal was created by Gary Mackay-Steven after he robbed Charlie Mulgrew on the touchline, and the winger was a constant threat to the home side.
He often troubled Adam Matthews, but the full-back was not always in a state of flux. He executed a perfect sliding tackle on Johnny Russell to retrieve one situation, although Bobby Madden, the referee, penalised the full-back anyway for a tug in the box that did not appear to happen.
Any anger flared only briefly, since Jon Daly's penalty was saved by Forster. "I wish Bobby had been refereeing on Tuesday night," Lennon said. "I have seen it again and there's no contact."
Lennon could be wry, since his team had played as if focused on restoring the mood of the crowd, with Joe Ledley scoring a third goal before half-time with a shot that deflected off Sean Dillon.
Izaguirre attacked incessantly down the left and Commons was always inventive, while Gary Hooper and Anthony Stokes combined with their familiar understanding.
The latter, in particular, was effective after the break, winning the penalty from which Commons added the fourth – "It was a clumsy challenge [by Barry Douglas]," said Jackie McNamara, the United manager – then scoring twice himself.
Stokes' goals were a measure of his ability, with the first coming from long range and the second a poacher's finish after James Forrest's header had been blocked by Radoslaw Cierzniak. Stokes' contract is up at the end of the season, although Celtic have an option to extend it.
That seemed unlikely while the striker was out of favour, but he could yet play his way back into significance: "It's up to Anthony," Lennon said. "If he keeps playing like that, it's not a difficult decision."
United scored a late consolation, through Johnny Russell, but this game was an indication of the work that McNamara needs to carry out. "There was a bit of acceptance from some of our lads which I wasn't happy about," he said. "We have to take more responsibility. The back four played like individuals at times."