That is BS. Domestic companies have to compete with each other. The same mechanism that apply to trade with others countries applies to domestic manufacturers. What you are saying is you have no faith in the American economic system to produce the best products for Americans. I don't call them Free Traitors™ for nothing, it's well deserved moniker.
Not BS. Look at the auto industry in the 30 years after WW2. No, of course they weren’t protected...they didn’t have to be, we (or the Germans or the Russians) bombed their competitors’ factories into dust, and pretty much devastated their economies to the point that they couldn’t produce any decent autos for several decades.
So, what did this tariff-by-bomb produce here? GM, Ford and Chrysler DID compete with each other...to see who could produce the crappiest cars and still sell them to the American public. OK, so that’s a bit of an exaggeration...but not by much, since the Germans and Japanese came along in the late ‘70s and ‘80s, and damned near drove all of Detroit into bankruptcy. The simple fact is that even with competition, having a tariff or other barrier to entry for competition (even a barrier created by cratering your competition’s factories) produces LESS competition. The Big 3 are not the first, nor will they be the last, to act in this manner - aided and abetted by their own collusion, and their lobbyists in DC.
Again, I’m for consumption taxes leveled evenly on all participants, as opposed to income taxes. But tariffs produce only short-term benefits for domestic companies, while shorting the consumer. They are best used, IMHO, to get foreigners to reduce their own tariffs, so as to really allow the free market to work (which would lead, IMHO, to a great deal of prosperity here, as I most certainly DO have lots of faith in the abilities of our economic system).