That's the problem. Real humans in real world cannot be impartial and will always have biases. So if you expose the public to many different biased opinions and let them learn to recognize the biases and see past them, the "cumulative mindset" will be more objective and less prone to manipulation.
But if you let one biased group decide what the majority is allowed to see, the public opinion will inevitably align with the interests of that group, and won't be necessary beneficial to the public.
Have you noticed how in the past decade or two we have totally abandoned the pursuit of happiness through self-reliance and independence? How being depressed and outraged is normal, and is all but encouraged. This is all coming from the media actively shaping what gets into one's attention span and it will only be causing more and more misery with no end in sight.
And this comes down to a very simple formula. Media likes people who will create content for free. People who are willing to do are often unhappy and have a mindset that causes unhappiness. Media broadcasting their content (to their own profit, of course) is popularizing that mindset and making more people miserable. Bingo!