Diversity is the key to an effective and balanced media. Without diversity one person or group monopolising the media, running the risk of eliminating the human right of Freedom of Speech.
Fox news (owned by media mogul Rupert Murdoch) is an example of one person controlling the media. Fox is seen as having strong right wing views which they push onto their audience by restricting the amount of information/viewing time of left wing ideas. This restricts an audiences exposure to certain topics.
Let me take one of my favorite media platforms as another example, Reddit.
Reddit is a shining example of a failed democratic media site. The site is developed so majority rules, things are posted the ‘good’ posts get voted up the bad get voted down. However, users have come a custom to what gets voted up and conform to that thinking. Although the voting system is a good idea in theory people are beginning to use it for personal opinion. Thereby, anything that has been voted down shifts down the page so it is less likely to be seen. Due to this voting system and people becoming accustome to it, the same ideals (upheld by the majority of people on the site) is most viewed while the minority has little to no voice.
Although both these examples share different views, imagine if these (and more) all had the same ideals, or were controlled by one person or company. This is why it is important to know who provides your media; you must question what you are exposed to.