> The implication being that without such laws, enslavement of children, poisoning and maiming of workers, and other horrors would be totally legal in America?

Perhaps you don't recall the number of years in which slavery was legal in the US?

Or the years in which child labor was actually used?

Or the years in which a 40 hour work week wasn't normal?

The only way I'm able to understand how ANYONE can believe everything would be hunky dory without labor laws is if they haven't been educated in the history of this country (or any other country).