You should be skeptical of people who questions widely agreed historical facts as well.
We all might have been saying things like "it's a good thing we killed all of those fucking jews, it definitely saved humanity from being tainted" without anyone flinching.
This is the kind of stuff you still hear in neo-nazi circles. But imagine -- if we all thought that.
It sure is poetic how little of a choice we have in our opinions and world views, yet how passionate we are about them. Most people reading this right now would never think themselves capable of thinking such a thing.
If things turned out differently, the accepted world-view might be that certain lineages are tainted and that they reduce the pureness of people -- it may have been punishable to even dispute this.
Anyways, perspective.