I do not remember my parents ever lying to me, and I have tried to always tell my children the truth as well.
I never remember my parents swearing at anyone or about anything. They were honest when they were angry or upset, but did not feel it was helpful to get demeaning or curse things or people. I have also tried to help my children work out their problems and anger without resorting to shouting or swearing, because I agree that the escalation is more hurtful than helpful. We don't always succeed, but that is the goal.
When our textbooks glossed over the truth or TV programs misrepresented reality, my parents pointed it out. I have done the same with my children. When we asked about sex, drugs, alcohol, my parents explained it straightforwardly and also explained why they had chosen to remain virgins until married, and not risk addiction to mind-alerting substances (or even health-altering tobacco).
Santa Claus and the Easter Bunny were always fun imaginary characters. Jesus was a historical person, whom, my parents honestly explained, some people considered just another human being, but that a third of the world's population considered something much more, themselves included.
I have similarly tried to tell the simple truth to my children. What is lost by that?
As to religion, my parents said that they believed that God really does exist and that the Bible is a historical record of man's interactions with a real God. But they did not hide from us, even when we were very little, the fact that there are many people who think God does not exist, and that it is really only the personal experience of God for oneself that can "prove" his existence (and the existence of a spiritual realm) to an individual. They pointed out that if a person has never experienced God, he has no reason to believe God exists (unless he wants to accept the testimonial of others who have as proof enough). As a result I was able to be honest when I myself had not yet encountered God, and never look down on others who had no reason to believe in him having not encountered him.
I always felt free to challenge my parent's values and perspectives because they did not demean opposing opinions, but explained clearly and directly why they had chosen the path that they were on. They practiced what they preached. I have tried to do the same with my children (now all in their twenties).
My children have the advantage of seeing the honesty of my parent's lives as well as my own and my husband's. When my mother got cancer, we sat our kids down and told them everything that was happening... they knew about the chemo and the pain and her 5 year fight to live was played out before their eyes. On her death bed my mother asked my second son about the paper she had been helping him research for college. He knew her body was soon to stop functioning... and that while some thought her spirit was also about to end, none of us believed that was true. We burned her body, scattered her ashes and rejoiced in her release from pain into eternal life.
I believe if parents do not think that heaven exists they should tell that to their children the first time they ask. But they should also tell them that many others believe heaven does exist. Or vice versa. That would be telling them the truth.
Perhaps my parents were so straightforward because they were highly educated (my father graduated from Caltech (BS), Columbia (MA), Cornell (PhD) and Princeton Seminary, my mother summa cum laude from USC), so intellectual honesty was important to them. Or perhaps they were honest because they believed in the moral obligation of truth because of their faith in a moral God.
Whatever the reason, I would like to affirm to all parents that truth works. Be honest about why you have chosen to believe what you believe and live how you live. Be honest about the mistakes you have made and are making. Kids can handle truth delivered compassionately. What they need is a strong relationship with you and each other, and that cannot be built on deception.
You ignore (at least in this post) the millions who were not raised like you, and yet have strong relationships with their parents. You ignore parents who've actually had to answer some really difficult questions ("What's a prostitute?"). You ignore the fact that you can't correct all the lies and half-truths because you won't hear or see everything your child hears or sees.
Even the truth as one "believes" it comes with bias, which one might consider a lie. "I believe in God, but some people don't believe he exists because they haven't had a personal experience of Him" ... the truth, perhaps, but it conveys an unmistakable opinion; how does one's 8 year old truly infer "God may or may not exist" from that? Is that really "truth" if you nudge someone so perceptibly in the direction you want them to go?
It's quite convenient for you that they were right on all the things they taught you. Or were they?