This is an "ad hominem fallacy." The attributes or beliefs of the entity making an argument are entirely irrelevant to whether the argument is correct. The argument must be evaluated solely on its own merits.
They've failed to analyze the merits of the article sufficiently. They are, in fact, committing the "ad hominem" error -- they see what appears superficially to be a trustworthy news site, and they believe it unquestioningly, based on the supposed authority of the source, rather than independently evaluating the claims being made.
