What is the macro theory of media?

The macro theory of media revolves around the effects of media messaging on the general audience, as opposed to the micro theory, which involves effects on individuals. These two effects are, of course, interrelated, but joining with others who support one's ideas enables what psychologists refer to as cognitive consonance—the idea that a person has made a good decision based upon the observation that others have obviously taken similar decisions.
Perhaps the most important element of the macro theory is the way in which it frames an issue. That framing may lead, in turn, to an audience changing or adopting a belief which may be false or counter-productive to society. Examples of framing may be found in the speech and writing of political parties and special interest groups which have a message to promote, whether one of policy or person.
The intent of framing may be immediate or long-term. For example, in a local political campaign, the goal is to get someone elected or to stop the election of someone else. The results are relatively immediate, in that such a campaign may only last for a few weeks or months. Long-term framing might include such ideas as gun control or women's rights. The NRA, an organization that is many decades old, has re-engineered its message over those decades with the result of fully linking itself to the Second Amendment of the US Constitution, making opposition to its goals seem unpatriotic.
Modern media has many ways of delivering messages, both hard-copy–based and in virtual formats, along with TV and radio. There are also an abundance of informal channels for the dissemination of information. Viewers tend to choose their TV news media outlets in sympathy with their beliefs, and the same applies to radio and print journals. Media shapes public opinion and is also shaped by it. Whether consciously or unconsciously, they are part of a social structure that sets the agenda—that tells people what's important and what to think about those important things.
The informal media is best represented by what is called the "blogosphere." Bloggers can have a significant impact on public opinion without the sort of established editorial controls extant in traditional media outlets. Unlike the traditional outlets, blogs tend to be highly focused on a single issue or a single point of view. Those they claim as followers of their messages are among the most ardent supporters of those single issues. While some blogs may lead opinion on popular music, film, or food, others may lead opinion on civic or political issues, such as those supporting white nationalism.
An important feature of the macro theory is implied by the paragraphs above. When a person finds a group that supports his or her issue or point of view, it helps him or her not only by adding the group's content or facts to his or her own, but by creating a platform by which to oppose contrary points of view. In some cases, this fosters debate between the opposing sides—a socially relevant outcome. In other cases, the platform is used to quell opposition—to obfuscate or silence the opposing message. Donald Trump's team used this to frustrate the Clinton campaign, as did Hilary Clinton's team to frustrate Trump's.
In summary, the macro theory of media is based on group dynamics. It attempts to frame a message for either short- or long-term gains, set an audience's agenda, and intimidate opposition. In an environment of competing facts, it may be very important to recognize these elements and work to seek the truth.