A naive but well-intentioned lad seeking to root out bias in the media might base his argument, as others have done, on a right/left dichotomy. He may focus on the distribution of positive and negative coverage, or he may look at numbers that show the political self-identification of journalists. He may also take a methodology that assumes there are "two sides" to every story and categorize coverage of specific issues as "one sided" and therefore needing a perspective adjustment. All of these methods fail at the conceptual stage and should not have been employed, because each begins with a tacit and indefensible assumption that bias can be identified merely through comparison to other bias. Unfortunately they are employed, and this makes me sad.
Suppose one were to use this method to evaluate the bias in the statement that 2+2 = 4. One would begin by attributing "2+2 = 4" to a mathematicial perspective and "2+2 = 5" to an alternative perspective. One would then conclude that our discourse surrounding addition is biased toward - or by - mathematicians. This is possible with any statement using any pair of perspectives. The method gives no insight to the truth or veracity of the claims in question.
When applied to a political issue we are left with the same type of conclusion. The problem is that bias is a term that implies two conditions. The first is that a biased perspective is some source of information that conflicts with other information available. The second condition is that a biased perspective is in some way methodologically flawed. Our argument from the previous paragraph, and the arguments encountered in the media tend to just look at the first question. There is no discussion of methodology. Therefore there can be no claim that the "biased perspective" is in fact not the best or most useful information available.
To further illustrate, suppose a detective investigates a murder. There are three suspects. His investigation initially finds evidence against each of the suspects. However, he concludes, from a careful examination of all of the evidence, and through further investigation, that only one of these three suspects is guilty of the crime. It would be misleading in this case to present an untrained opinion that conflicts with that of the detective as "evidence" of bias by the detective. The accusation of bias implies that there was a problem with the methodology used in the investigation, but no evidence of that has been presented.
The buzz of speculation that there is bias in the media is therefore completely without merit. Similar accusations that the academic world is liberal and that scientists are anti-religious fail on the same ground. The debate about policies and world events should focus on the methodologies. Once he has considered these methodologies objectively, it will be clear to the investigator that liberals are mostly right. The truth itself, and the best and most effective policies are not things that can be described as biased. Academic methods, long scorned in public policy, will have to take the fore in the coming years because the situation for humanity will soon be dire.