When the retired neurosurgeon first declared his candidacy in May, the networks gave it just 56 seconds of coverage. The networks began covering Carson more intensively after the first GOP debate; in September and October, Carson received more TV news coverage than any Republican candidate other than Trump.
As they do with Trump, the networks have highlighted what they see as controversial statements from Carson, such as his comments following the Oregon school shooting where he advised potential victims to fight back, and his statement about gun control making Hitler’s Holocaust more likely. Such controversies amounted to 41 percent of Carson’s coverage in October, a higher percentage than any other GOP candidate, including Trump. http://www.newsbusters.org/blogs/nb/rich-noyes/2015/11/07/mrc-study-tv-news-trying-winnow-field-gop-candidates
That study backs up what many people have noticed about Carson being targeted by Democrat news companies (most news companies).