Challenging your own viewpoints is not just hard, it's downright dangerous. You can really lose your sense of identity and question your own morals if you are not well-grounded. It's much easier to dig your heels in and try to limit your self-reflection to be more "safe". (I still think you should question your viewpoints, but I don't blame people for being a little afraid.)
This is especially true if you have a history of being somewhat cruel to people on the basis of a conclusion you're not really 100% sure you agree with anymore. Now if you question it, you have a lot of guilt to contend with.
I would say as I've gotten older, I've actually tried to be a little more grounded in my beliefs. Our political world is so crazy, that I think sometimes, it can even be hard being committed to basic kindergarten morality. "Look at all these bad people doing bad things and being successful, maybe I should do bad things to be more successful" is a challenge to your viewpoints that is worth cutting off at the roots.
I suppose, but there is no such thing as objective morality, it's all subjective. That’s not to say people shouldn’t feel guilt or hesitate when evaluating their past actions, but we often act based on the best framework we had at the time.
Morality evolves, both personally and culturally, and trying to hold a static identity in the face of that change just leads to more internal conflict. It’s uncomfortable, yeah, but clinging to certainty for safety’s sake can be more corrosive in the long run.
OTOH, I am the kind of person who feels great joy in discovering that I have been wrong about something, I have learned something better, and I have deepened my understanding. It could be about anything. Challenging my viewpoints is very enjoyable.
It surprises me that most people don't seem to feel that way and I struggle to understand why. Apparently, people often feel angry and alienated by the truth. I think that never makes sense, but I've learned to accept that people simply feel threatened by the truth sometimes and I can't usually convince them otherwise.