Go read some Peter Navarro. He explains desperately how important it is to be protectionist (to a limited extent) with certain industries. Especially if they link to security and health of the nation. You do not want a hostile nation to make all of your pharmaceuticals. You do not want them to hold you hostage over your lack and their surplus of steel. This is basic, basic stuff.
And the whole point is that other countries are not engaging in fair trade practices. If they aren't engaging in fair trade, then they can't engage in this fabled myth of "free trade". This is literally the Trump trade doctrine. He has spelled it out and acted on it. If the CCP hadn't manipulated the price of steel to wipe out American steel producers, they wouldn't be subject to extreme tariffs. Simple, simple stuff.