This grift is the engine of Handwaving Freakoutery that runs the modern dialogue.
"Look, there was a white nationalist this one time" runs Left Twitter, just like "look, this SJW wants to cancel Christmas" runs Right Twitter.
Nutpicking. The amplification of nuts and elevation of them as the standard to which you oppose is a kind of a strawman except you're using real people saying real things. Both sides do it, because it's really, really easy.