> Offering a lower price to consumers than your competition is not coercion against a competitor.

It is if you are offering a price lower than your costs which you offset by cash from earlier deals, which the new upstart cannot do. When the new upstart is bankrupt you push the price higher, because now there's no competition anymore. That's the reason such stunts are forbidden (at least in civilized countries).

And when you go bankrupt because you're unable to run your business, you'd consider that completely voluntary?

How is it not voluntary? I started it. I knew upfront I could fail. Has anyone else forced me to fail?

Once you start the company, you are subject to market pressures, and when another company can manipulate those pressures, they can manipulate you.

Indeed, even your decision of whether to start the company is influenced by the same market pressures.

If you can't profit off an enterprise, then there is not enough demand to justify your existance. If the market leader is going to undercut you to drive you out of business to then jack up prices to exploit consumers, assuming no artificial barriers to entering the market occur (mostly legal exploitation) or the price to entry is not too high, then as soon as they up their rates they reopen territory for competitors to arise.

In the end, if the market leader is constantly crushing competitors through undercutting to maintain their position, they are not really exploiting their customers at a monopoly and its a market win. It is still competition - the leader just moves to eliminate competition (which would piss off shareholders or anyone in general with a long term outlook on the company) rather than compete against it. As long as they cannot stop competition (and in a voluntary fair system, they cannot) then they have to deal with it one way or another.