The US rider's epic fall concluded Monday with the loss of seven Tour de France titles, leaving the sport grasping for a way to move past a drug-tainted past.
The International Cycling Union (UCI) supported the findings of the US Anti-Doping Agency (USADA), which branded Armstrong the central figure in a sophisticated, systematic doping scheme.
Fahey said those in charge at the time must bear some responsibility.
"There was a period of time in which the culture of cycling was that everybody doped. There is no doubt about that. The administrators have to take some responsibility for that," the Australian told ABC radio.
"Is that period gone? That's something which I think the jury is out on and I think UCI are meeting this Friday to consider a number of aspects, including what their response must be, going forward."
Pressed on whether he meant everyone -- literally -- in that era used drugs, Fahey replied: "The evidence that was given by those riders who are teammates of Lance Armstrong, one after the other, they said the same thing -- that you could not compete unless you were doping."
In all, 26 people -- including 11 former teammates -- told USADA that Armstrong and his team used and trafficked in banned drugs and also used blood transfusions, and that Armstrong pressured others to do so.
In a separate interview with Australia's Fox Sports, Fahey said cycling would only regain credibility when the senior officials on watch during the "debacle" were removed.
"Looking back, clearly the doping was widespread," he said.
"If that doping was widespread, then the question is legitimately put: 'Who was stopping it? Who was working against it? Why wasn't it stopped?'
"I think it's relevant to ask those questions."
Fahey added that anyone involved during the Armstrong years could not justify their place in the sport's hierarchy at the UCI.
"It's not a question of simply saying we'll rule off the line and go on," he said.
"They clearly have to take the blinkers off, look at the past, examine the people who are there, ask themselves the questions: 'Are those same people still in the sport and can they proceed forward with those people remaining?'
"I don't think there's any credibility if they don't do that and I think they need to get confidence back into the sport, so that its millions of supporters around the world will watch and support the sport going forward."
UCI president Pat McQuaid, who has held the position since 2006, on Monday warned against blaming the sport's authorities for the doping scandal.
His predecessor Hein Verbruggen was at the helm during Armstrong's reign.