I think even the most ardent free trader would agree that certain indsutries need protection because of their national importance. Various defense industries, for example. (I also happen to think there may be other industries deserving protection because of certain social values, but as this is a more disputable point, I want to focus for the time being on industries necessary for the national defense.) The necessity for protection is based not on economics, but rather on other policy considerations.
Given this necessity, what about industries that are necessary to produce the component parts that go into the defense industries? I'm way beyond my knowledge base here, but if we need, say, steel to produce weapons, and if we agree that our weapons industry is not an appropriate subject of "free trade," then isn't it at least possible that we need some baseline native steel industry? Even if economics would dictate that all steel should be made elsewhere while we focus on our alleged comparative advantage in financial services, etc.? And if so, how significant does our baseline production of steel need to be?
I should note that I opposed the Bush steel tariffs. In my view, there was no non-economic policy rationale given that outweighed the clear net economic loss to the United States. But that doesn't mean that I wouldn't support other, better-reasoned deviations from free trade dogma.