Thinking completely outside of our post-WWI bubble, history has been far more brutal in the past. This is the anomaly. Taken as a whole, human history has been full of genocide, slavery, brutality.
When somebody misrepresents "survival of the fittest" in the way that the 20th century fascists did, and embark on mass extermination "for the good of the world" (in their warped view), citing the fairly recent Darwinian view of evolution, isn't it better to tackle these views head on, for the benefit of those who haven't the inclination or the ability to think it through themselves?
What I see nowadays is a complete lack of curiosity. Nobody wants to try to understand why people "go bad", they just want to put them in the bin. That only works if those "bad" people are a minority.
Also, when the "good" people stop engaging in debate with the "bad" people, there's a danger of creating a dogmatic society. Looking at Christianity in the middle ages, and extremely confident sense of your own rightness can lead to atrocities too.
Sorry, probably nonsense, boarding a flight, not paying full attention to my post