Protectionism is not and should not be a bad word. Free trade does not necessarily mean unregulated trade, any more than a free market should be a laissez faire market.
Protectionist trade policies of the US, in the form of tariffs and quotas on certain imported goods, and certain subsidies, was in the past beneficial for certain manufacturing sectors, by ensuring fair competition between locally manufactured goods and imported goods. I grew up in the Steel Rust Belt, and was witness to the decline of the heavy manufacturing industries in the Midwest, and the effect it has had, and is still having on the economy of the nation today.
In my admittedly biased view (my father and older brother were union tradesmen, and my grandfathers were both union organizers), I think the collapse of the heavy manufacturing industry (steel, automobiles, industrial machinery, railroad, and others) was either brought about or sped up by the loosening of restraints on the importation of steel from Japan. This was the beginning of a trend to “export jobs”, by manufacturing items or parts overseas rather than here in the US.
It is not only for political reasons that labor unions have traditionally upheld strong protectionist tariffs. Support for locally (US) manufactured goods have historically led to stronger wages and benefits, and high employment.