I can see that in a way - if you've always thought one thing and then find out something different, it makes you question everything else you held true. It's especially hard when it's someone as close as your own father. Conversely, one would think centuries would soften things - I did a little checking for a friend who has an interesting family history, and found out that an ancestor from the 1700s had spent time in jail. No record of why - could have been major, could have just as easily been as minor as taking a loaf of bread to feed his family in that timeframe. But my friend's father was very displeased when she told him, and refused to believe it.