The 63-year-old actor, whose new BBC drama series 'Quirke' is set in 1950s Ireland, recalled an incident when his mother, who was pushing him in a pram, stepped off the sidewalk into the road to make room for a priest.
"It was almost a Taliban-esque society," he said. "That's how much power they had. Now all the rocks have been lifted and all the maggots have crawled out. The Catholic Church is a tyrannical, evil institution, there's no doubt about it – anti-woman, anti-homosexual, anti-love, anti-condom, totally elitist."
In 2011, the actor revealed on an Irish chat show how he was sexually abused between the age of eight and 11 by Christian Brothers in the Roman Catholic seminary where he was studying to be a priest.
"I didn't think it severely impacted me at the time," he told broadcaster Gay Byrne. "But when I think about my later life, and how I had difficulties with certain issues, there is a real possibility they could have been attributable to that."
Now he says, "Whether the Catholic Church attracts paedophiles or whether the Catholic Church itself breeds paedophiles, I don't know the answer. But because of this culture of secrecy, and because there's no accountability, priests – and nuns – could commit crimes against children and realise they didn't have to pay for it – the Church would never hand them over to the legal authorities. I think anybody who betrays the trust of a child deserves to be punished.
"A child doesn't have the understanding of the world to know what's really good or bad," he continues in this generalised vein. "As far as they're concerned, what an adult tells you to do is the right thing to do, and to take advantage of that is a crime against the soul of a child," he told the Independent.
The actor, who now resides in the United States, had to return to the Dublin of his youth to film the BBC's adaptation of John Banville's 1950s-set thrillers, written under the pseudonym of Benjamin Black.
Byrne said the experience was like "crashing into the past."
"By absolute coincidence we filmed in the very first apartment I ever had, on Pembroke Road," he says. "We shot in the theatre where I made my first professional appearance – I hadn't been in there since – and to walk into it… phew! Déjà vu doesn't begin to describe it."
'Quirke' will air on BBC1 later this fall.
Here's a trailer to "Quirke":