Can it really be so hard for writers to understand that supporters of slavery and genocide could rationalize their own actions in the same way?
They ought to try reading some of the arguments for bonded labor in Pakistan, such as those featured in the interviews of slaveholders found in the analysis of modern slavery in Kevin Bales' book Disposable People: New Slavery in the Global Economy. "It's for their own good" is one of the most difficult-to-disprove logics, as it's usually based on stereotypes and racial/religious/class profiling, and yet one of the most common.
"It's for their own good" sounds sort of like Aristotle's supposed argument in support of slavery -- his argument was that for so-called 'natural slaves' (i.e people who have what he calls a slave-nature) they are actually better off being controlled and told what to do by people who know (better than they do) what's best for them. The interesting thing about Aristotle's argument is that we can't really tell whether he was in fact arguing for or against slavery (i.e. he could have been saying "it's only ever justified for people who have slave-natures, and there are no such people / or it is impossible to ever determine for sure that anyone has a slave-nature").