On a personal note, it didn't take very long to question the truth/reality of what my parents said and taught me. It took a bit longer to begin to develop and more or less trust my own opinions and views. I've found that it has become more difficult to develop hard opinions as I've grown older. Things are so complicated and there are so many people who seem to want to influence my views and opinions and I suspect some of them are quite good at it.
I suppose that there are two realities for most of us. The first I suppose is objective reality, true physical reality. Then there is perception... the reality we perceive through our own personal lens we develop through personal experience, ideals (what we want to believe), and what has stuck with us from our early years, what you refer to as nurture, I think.
I'm sure that I sometimes mistakenly confuse my opinion with fact. I'm not sure whether that statement is fact or opinion