As I mentioned the other time the Wiesenthal Center was brought up, you have one group of political activists endorsing another. This does nothing to establish Berlet as a reliable source, in fact, it underscores the problematic nature of using him as a source (per WP:NOTADVOCATE.) With respect to Newsnight, the Berlet material is an interview, and Wikipedia considers interviews to be primary sources, which should also be avoided. In an interview, there is no fact checking or any of the other features that characterize a WP:RS.