It's feeling, rather than thinking.
They get uncomfortable thinking about biological hierarchies and the implications that they carry, so they fixate on the >
I know [some small percentage of X population] and they're totally awesome, so obviously [group X] are ALL like that!
line of thinking because it's a hell of a lot less scary to them than the policy implications of culture or biology driving certain populations towards antisocial behaviors that are a net negative for civilized society as a whole.
On the bright side, that more or less also proves that they understand and believe that inferior and/or more destructive members of a society must be culled or otherwise removed from that society (which is why they are so afraid of acknowledging biological hierarchies in the first place) which means that once the truth is undeniable by them, they will likely become rabid footsoldiers for the cause.