I had these types of discussions with family and friends at a young age. - Could it be because I am Jewish and Judaism has a tradition of learning through discussion and debate?
Isn't it better for children to learn to think critically at an early age, rather than have to unlearn things when they are older?
Well I think it depends on your definition of "young age". I don't know anything about Jewish traditions, but where I come from,
children are not taught to debate anything with adults. I would have been in serious trouble for that because it is considered highly disrespectful. As an older child (teenage years), we debated things all the time in school...and I did find this a very helpful learning technique. I know there are advanced children in the world, but in general, if you walked up to an 8-year-old and said "Do you think we should apply modern ethics to past historical events?"...I believe they would have a hard time grasping the concept, even if you worded it differently.
Also, I don't think there is anything to be "unlearned", unless you (or the teachers) are actually lying to your children. Children are taught a "basic" history, which is elaborated on when they are old enough to comprehend the more intricate details. I grew up being taught that Columbus was an explorer...that is a fact whether he did bad things or not. I don't think my daughter at 5-years-old (or 9 or 10) needs to know that he raped children and enslaved natives. If these kids were in high school, I don't think it would be such a big deal.