It was a decision that seemed out of kilter with all the evidence from three rounds of boxing in which Conlan had looked the more accomplished fighter.
Concern about the probity of Olympic judging had been raised before these Games in an English newspaper - that debate reaching a new crescendo on Monday night with Russian heavyweight, Evgeny Tishchenko, inexplicably getting a verdict over a Kazakh boxer, Vassiliy Levit, having looked outclassed.
Now Belfast's Conlan - the reigning World, European and Commonwealth bantamweight champion - was gone too, meaning Ireland's Olympic boxing challenge had ended without a medal for the first time since Athens 2004.
If there had been some anger within the Irish camp over Katie Taylor's split-decision loss to Finland's Mira Potkonen on Monday, Conlan's defeat took that indignation to another level.
His father, John, interjected "shame on them, shame on them" as Michael articulated his frustration afterwards in the mixed zone. In the immediate aftermath, Michael himself had given the finger to ringside judges, labelling the governing AIBA "corrupt".
Last night, there was word of a movement growing against that body, with Irish, British, Canadian and American officials said to be meeting with a conviction that there has been something fundamentally amiss with the boxing judging at these Games. Before Rio, one Irish judge, Seamus Kelly, revealed that he'd been told to cheat at the Arab Games in Doha in 2011.
He said that, having raised the alarm to AIBA President, Dr CK Wui, in an email, nothing happened - and he had effectively been sidelined by the body.
In response, the AIBA claimed that Kelly's allegations were baseless", accusing the Irishman of "erratic behaviour".
A Canadian, who pulled out of officiating in Rio, cited the "blatant corruption" of the process as his reason for doing so.
In Riocentro Six yesterday, the rising decibels seemed to trumpet a consensus that Olympic boxing had some pretty grave questions to answer.