Not exactly. It's fundamental to specific flavor of western democracy that has become common in the world, at least on paper.

But you can have democracy without it. In fact you can have democracy with lot of other characteristics that seem weird today, like randomly chosen representatives, slavery, exile etc. It's largely orthogonal.

This is not about democracy. This is a private company.

If Whole Foods doesn't have to hold a public tribunal to ban someone from their store, then ISPs don't, either.