This is exactly the mindset it takes to let atrocities happen and scarily, it's the thing that most appeals to people about Trump - he reinforces for them that they are the "real Americans" and anyone else is an interloper. People in the R party such as Mike Pence who are calling now for "unity" need to take stock of how often this sort of divisive rhetoric has been used to whip up followers and decide whether they actually want unity or not.