I believe you are conflating their point. They aren't advocating fining for ethical violations, but fining on the basis of realized damages. If you think both the company and workers are responsible for those damages, it is unethical to disproportionately fine only one side.
If you tax the company, both sides will be affected. The company directly through the fines, but also the workers indirectly as the company pay structure will have to adjust to remain viable. If you only tax the workers, only one side of that equation is affected.
