> the "use of it" is obvious, it's another protectionist tariff in a long, long line of protectionist tariffs

I’d be curious for contemporaneous accounts over someone a century later guessing what may or may not be obvious. Maybe a cabal of industrialists conspired. The Foreign Dredging Act does predate trustbusting. Or maybe there were military concerns. Not an issue in this particular case, but one can imagine outrage if e.g. China controlled the world’s dredging fleet and threatened to isolate America’s ports in retaliation for some Senator’s mean tweets about Xi.