It's perfectly fair to judge someone by the accounts they follow and retweet approvingly. Concannon follows dozens of white nationalist accounts, so the most likely conclusion is that he at least has some white nationalist sympathies. That doesn't happen by accident.
Comparing his behavior to the "one-drop rule" is ridiculous. The "one-drop rule" was about a person's heredity, not behavior. Given the sheer number of hate accounts that he follows, there's a lot more than a drop here.
It would be great if white nationalists were honest about their views. But often they hide there extremely unpopular opinions. It's clear that Concannon has a white nationalist agenda, and I'm going to keep pointing that out despite those who would try to launder his extremist views.