There is no record of whether they had to repaint the walls after his postmortem was over that day, but it wouldn't come as a surprise.
Celtic had just been embarrassed in the 2010 Scottish Cup semi-final by Ross County, who finished in the middle of the Irn-Bru First Division that season. It was Lennon's first major setback and it looked like it might cost him the chance of permanently landing the Celtic job.
His reaction was incendiary. The anger wasn't channelled against County, or the referee, or any of the other scapegoats beaten managers usually turn on, but at his own players. He eviscerated them.
"It has been a shambolic season," he said, spitting out the words. "They are nowhere near good enough. I am sick of seeing strikers not wanting to go in where it hurts to score a goal for the team. We can't keep clean sheets, either. We're too soft. I'm way past angry with them. Whether I am here or not next season, I told them that I am pretty sure some of them will not be."
That was the first of many. His job was on the line back then but Lennon has been no more forgiving of poor performances as a rock-solid Celtic manager than he was as a vulnerable caretaker. Scathing criticism pours out of him when he has come to the conclusion that his players haven't pulled their weight. After losing 4-0 to Utrecht in 2010: "I can't defend the indefensible."
In 2011, after St Johnstone won at Parkhead. "I'm angry, really angry. Our players need to toughen up mentally. We were complacent and wasteful in front of goal. In the final third we were awful. Our front six were bang average, to say the least."
After drawing with Hibernian at home last season: "I don't think they're giving enough. Some players have given everything and carried the torch but others are happy to go along riding on their backs and not making the contribution I want."
Hooper and Stokes? "I thought the two of them were poor."
After losing this season's Scottish Communities League Cup semi-final to St Mirren: "It was soulless, it lacked intensity, desire, will-to-win. Some of them behaved like spoiled kids out there. I perceive them to be top-class players but maybe I've got it wrong. Maybe I need to look in the [transfer] window and change things."
And then, bringing us up to date, another bloodletting after they lost at Motherwell on Wednesday. Had they been complacent? "If that's the case then they won't play here. They can go and find another club and I'll play the kids. It seems to me if we leave Gary Hooper out of the team then we suffer." Motherwell's winning goal? "A comedy of errors." Most of Celtic's strikers? "Insipid."
Most managers are nowhere near as publicly hard on their players. But he doesn't just voice these maulings as a knee-jerk reaction to losing. Celtic have been beaten in Europe, or by Rangers, and he has been pretty forgiving to his side. Or they've lost to Hearts, or in last season's League Cup final to Kilmarnock, and he has (more predictably) let rip at the referee.
When Inverness Caledonian Thistle won at Parkhead in November he thought the result so unjust he defended his men, even getting into a row with a Celtic supporter and threatening to resign if that's what the majority wanted. "I didn't like what they were saying about the team," he said.
He was equally prickly when Murdo MacLeod had things to say about going out of the League Cup to St Mirren. "I have a right to be critical," said Lennon. "I think I am the only one who really has a right to be critical of the team when they perform like that." As he knows well enough, it doesn't work like that.
But here's the thing: Lennon's outbursts have an effect beyond making vivid headlines. There is an obvious danger of repetition reducing their effect, but so far they seem to have worked, giving Celtic the kick up the backside he believes they need. After that Ross County debacle, they won all of their remaining six league games, a sequence of results which landed him the job on a permanent basis. After that Hibs 0-0, they lost only one of their next 25 games. After losing in the cup to St Mirren they scored 10 goals to win their next three games. After Motherwell last midweek they were sharper and more convincing when beating St Mirren to ease into today's William Hill Scottish Cup semi-final draw.
His new ally, Sir Alex Ferguson, was the master of premeditated "rage", delivering his infamous hairdryer treatment to someone only to turn away and sometimes give a conspiratorial wink to a bystander. It felt convincing enough to the trembling victim, of course.
Lennon's tendency to erupt against mediocrity looks authentic. He isn't likely to lose the rag if Celtic lose to Juventus – realism suggests that they probably will – but it's likely he'll be stripping paint off the walls again soon enough.