From the ADL special report "Rage Grows In America: Anti-Government Conspiracies":
The most important mainstream media figure who has repeatedly helped to stoke the fires of anti-government anger is right-wing media host Glenn Beck, who has a TV show on FOX News and a popular syndicated radio show. While other conservative media hosts, such as Rush Limbaugh and Sean Hannity, routinely attack Obama and his administration, typically on partisan grounds, they have usually dismissed or refused to give a platform to the conspiracy theorists and anti-government extremists. This has not been the case with Glenn Beck. Beck and his guests have made a habit of demonizing President Obama and promoting conspiracy theories about his administration.
On a number of his TV and radio programs, Beck has even gone so far as to make comparisons between Hitler and Obama and to promote the idea that the president is dangerous.
These kinds of claims from Beck create an intersection between the mainstream and the extreme. They play an important role in drawing people further out of the mainstream, making them more receptive to the more extreme notions and conspiracy theories.