Corporations are not exempt from this. A libertarian would support using force to stop a corporation from using force to coerce people to do something.
But Libertarians reject a premise that a corporation is required to serve you. You can opt-out and the corporation should leave you alone. But you are not entitled to service or employment from that corporation. Your rights cannot depend on the performance of another. I have a right to produce or purchase my own food, but I do not have an right/entitlement to food that I have not purchased or produced.
How can an individual or even a group of individuals stop a corporation from underpaying its workers so that they need to use some public assistance, food, or medical care?
There are many similar examples, but they all boil down to the asymmetry of power. An organization capable of employing many lawyers, or even a single good one, can grind you down until you have nothing left. I still see libertarians as having no answer.
I think the only way to fight back against corporate abuse is to build a stronger center of power. Something like a union, a citizenry willing to take collective action, or even a Government that is not beholden to corporate interests.
For example, regarding pollution, prohibiting any discharge of the offending pollutants, or measuring and taxing them in some way - but with no requirements about HOW a corporation should meet these regulations or otherwise run their business.
Unions are fine, and people should obviously be free to join them if they want. But there should not be any laws that require or favor unions, and government employees should not be allowed to unionize.
A government beholden to corporate interests doesn't matter much if the government doesn't have much power. But with power comes interests and influence, always.
