Rush Limbaugh may have a substantial audience base but his involvement in a story allows his critics to readily disregard whatever he is presenting. He is not an accepted member of the media profession. He has received a broadcasting award and been savaged in the introduction speech for the same award.
President Clinton was able to quickly demonize Rush's profession. Mike Drudge is also not a "credentialed" member of Big Media.
The talking heads on the alphabet networks and at "trustworthy" papers like NY Times and Washington Post are considered "dependable" members of the media.