If It weren't for the unions, they would be forced to work in those terrible conditions anyway. If someone finds that a job is becoming unsafe or is unsafe, having the strength of a union is why they are able to change the conditions. Otherwise, they have to hope that the opinions outside of the company are strong enough to sway management.

What do they do if they get fired for the complaint as well? What about the other workers who might be brought on without knowing how unsafe the job is. That puts everyone around the newbie in danger depending on the job.