Bennett appeared to have taken the stage, his second of the Spanish Tour so far, but a review by race jurors after the finish found the Irishman's double shoulder barge on Trek-Segafredo's Emils Liepins in the lead out to be overly aggressive, awarding the stage to Bora-Hansgrohe's Pascal Ackermann instead.
And Lefevre was not happy with the decision, clashing with Trek boss Luca Guercilena in an angry rant while also openly criticising the UCI video review system.
After taking Stage 4 of this year's Vuelta, Bennett went into Stage 9 as a clear favourite and looked to have won as he finished ahead of Ackermann by over half a wheel.
Interviewed immediately after the finish and before the review, the Irishman expressed his happiness to have taken the stage in what would have also been his 50th career victory and 100th Grand Tour win for his Deceuninck-Quick Step team.
Seemingly referring to the incident with Liepins, Bennett claimed the aggression came from the other riders and not himself.
"I had to come from behind at speed," Bennett said. "It was a big fight, we had some guys nearly put us in the barriers trying to take the wheel which was a bit sketchy but we stayed upright."
The UCI issued a statement on the relegation, explaining, "The decision, taken unanimously, was based on television footage and taken as per article 2.12.007 of UCI Regulations sanctioning 'deviation from the chosen line or irregular sprint'. Both the rider and the team’s Sports Director have been heard by the Panel."
There's plenty to look forward on what shapes as the key weekend of the 2020 edition of La Vuelta a España - LIVE, FREE and in HD on SBS VICELAND and live streamed via SBS On Demand.