The 36-year-old was shown a straight red card in the 28th minute – with Celtic already a goal to the good – after racing from his box and clattering into Mohammed Sangare as the Livingston forward bore down on goal.
Referee John Beaton gave the former England stopper his marching orders for denying a clear goal-scoring opportunity, but Lennon felt the challenge alone, which was late and high, was worthy of a red card.
"It's reckless as well from Joe," Lennon told Sky Sports. “He's fully committed and you just can't make a challenge like that. In commentary they were saying it was last man, but it could have been for reckless endangerment of a player as well. It's a clear red card."
Hart's dismissal – his first in 737 appearances for club and country – failed to prevent the Hoops from claiming the three points as Reo Hatate's penalty opener was followed by second-half strikes from Matt O'Riley and Daizen Maeda.
"It’s never simple and straightforward but Celtic made it look that way,” Lennon added. “I thought they were outstanding today. That’s a real statement of intent for the rest of the season.
"I thought the way they handled the sending off in the second half was superb. To come away with a 3-0 win with 10 men for a long period in the game was magnificent. A total comprehensive victory from start to finish.”