Well, the whole world is shifting under their feet and they are upset, or in these two cases they were upset.
In maybe 20 years people of European heritage will comprise less than half the US population. The majority of babies being born in the USA are not of European heritage.
Life is getting harder and harder for almost all of us. Whole occupations that once paid well and were more or less the preserve of "white" men are neither ( taxi driving in New York for example). And of course bigotry is not socially acceptable while still proclaimed in many private conversations. Whatever turned these two into white supremacists with blood in their eyes I won't shed a tear for them but I offer my condolences to the families of their victims.