In an interview posted online Friday, Giuliani was questioned about his family and told the Christian Broadcasting Network, "I think there are some people that are very judgmental."
Giuliani has a daughter who indicated support for Democrat Barack Obama and a son who said he didn't speak to his father for some time. Giuliani's messy divorce from their mother, Donna Hanover, was waged publicly while Giuliani was mayor of New York.
"I'm guided very, very often about, `Don't judge others, lest you be judged,"' Giuliani told CBN interviewer David Brody. "I'm guided a lot by the story of the woman that was going to be stoned, and Jesus put the stones down and said, 'He that hasn't sinned, cast the first stone,' and everybody disappeared.
"It seems like nowadays in America, we have people that think they could've passed that test," he said. "And I don't think anybody could've passed that test but Jesus."
In the New Testament story, related in the Gospel of John, Jesus does not actually hold stones. The Pharisees bring Jesus a woman charged with adultery, reminding him the punishment for adultery is stoning. They are testing Jesus in an effort to charge him with breaking the law.
The Gospel reads: "But when they continued asking him, he straightened up and said to them, 'Let the one among you who is without sin be the first to throw a stone at her.'
"... And in response, they went away one by one, beginning with the elders."
Giuliani has insisted his family relationships are private. In 1968, he married his cousin, Regina Peruggi. They divorced 14 years later, and Giuliani obtained an annulment from the Catholic Church on the grounds that as second cousins, they should have received a dispensation to marry.
Giuliani married Hanover in 1984 and they divorced in 2002. He has been married to Judith Nathan since 2003.
Likewise, he says his faith is private, although he evokes his Catholic upbringing on the campaign trail.
He told CBN he believes in God and prays to Jesus for guidance and help.
"I have very, very strong views on religion that come about from having wanted to be a priest when I was younger, having studied theology for four years in college," he said. "It's an area I know really, really well academically.
"... And my personal view of it is I need God's help for everything, and I probably feel that the most when I'm in crisis and under pressure, like Sept. 11, when I was dealing with prostate cancer, or (when) I'm trying to explain death to people, which unfortunately I've had to do so often.
"So it's a very, very important part of my life," he said. "But I think in a democracy and in a government like ours, my religion is my way of looking at God, and other people have other ways of doing it, and some people don't believe in God. I think that's unfortunate. I think their life would be a lot fuller if they did, but they have that right."
Giuliani also addressed a cell phone call he took from his wife, Judith, last week during his speech to the National Rifle Association, an important appearance because Giuliani clashed with the group when he argued for tougher gun control as mayor of New York.
"And quite honestly, since Sept. 11, most of the time when we get on a plane, we talk to each other and just reaffirm the fact that we love each other," he said.
"Sometimes if I'm in the middle of a very, very sensitive meeting, I don't take the call right then; I wait. But I thought it would be kind of nice if I took it at that point, and I'd done that before in engagements, and I didn't realize it would create any kind of controversy," he said.