"The thing that terrifies me, because I think it's coming down the track to the rest of us now, is just how easy this flimsy veil that separates us from the brutes is torn down - and, once torn down, is impossible to put back," he said on Scottish Television.
Mr Ashdown recalled his Northern Ireland upbringing in an interviewed by the psychiatrist Professor Anthony Clare. His father, a farmer, was a lapsed Catholic and his mother a Protestant.
Asked if he thought of himself as an Irishman, he replied: "Yes, I do, and I'm proud of it." Mr Ashdown has been reading the biography of Daniel O'Connell, who not only secured Catholic emancipation in the 1820s and fought for Irish independence, but was the Liberal Democrat leader's great- great-great grandfather.
At the age of seven or eight, he said, he told school friends he was a Muslim "because it seemed easier". "They said to me, are you a Catholic Muslim or a Protestant Muslim?" He now counts himself a Christian and prays "every night".
The young Ashdown was given the nickname "Paddy" at school in England, where he lost his Irish accent. By the age of 15, he had realised there was "a terrible nemesis to come in Belfast" because of discrimination against Catholics over housing and jobs. He recalled seeing Ian Paisley preaching from a soap box in Belfast. "I remember him frightening me to death."
Mr Ashdown has come in for criticism from within his party for concentrating on the horrors of former Yugoslavia. He has made regular visits to Bosnia and was an early advocate of military force to help Sarajevo.
Tribalism, religious conflict and intolerance posed one of the biggest menaces of modern times, he told Prof Clare.
But he warned that the dangers of intolerance were not confined to Northern Ireland or Bosnia. "One of the things that worries me ... is that I begin to see signs of the same kind of thing in our own inner cities."Reuse content