Until the recent release of a private recording of hime being racist, anti-Semitic and generally losing his shit, Richard Spencer was the acceptable face of neo-Nazism. Newspapers wrote puff pieces, TV stations gave him a platform, all oblivious to the fact that he is one of Hitler's heirs apparent.
So what can journalists and editors do to avoid this happening again? One is to verify that people are who they say they are, and the other is to stop assuming that the people you are interviewing are acting in good faith when all the evidence points to the contrary.
Good Faith, Verification And Not Being Fooled By Nazis