There are a whole load of genuine human garbage that see the Trump campaign as a source of inspiration and opportunity for spreading a message of race war, white superiority, and outright fascism.
There are two real threats here. First, that these organizations are growing their membership and base of support. You heard that right, Nazis in the US are a growing force. Second, that many of the ideas and policies that they encourage are finding their ways into the mainstream without all the swastikas and less-than-popular images of outright racism.