Media is not merely a reflection, but a perpetuator of extremes. If everyone stopped using media, there would still be extremist, but they would be so far distant we wouldn't think of them or their ideas.

Here's a great interactive explanation of how this works: https://ncase.itch.io/wbwwb

Absolutely, only meant to point out that the media brings out the worst that is already in us rather than corrupting otherwise civil beings.

To speak even more generally, humans make tools that amplify our impact. Some of those tools make us better at being terrible, some make us better at being clever, some do both.