Private warships satisified the discrimination test well, in those open seas.
Where is a warship limited to open sea use or of using only conventional weapons? Even then a warship could threaten a land-based fort or port and there was nothing then that prevented shelling from killing non-combatants or the such.
Chivalry, honor, rules of engagement, honor etc. may have prevented or limited the use or effect of some weapons systems then but I see nothing in the Constitution that prevents them. Machine guns and artillery are only as discriminating as the operators and the ammo used.
The Constitution does not have a threshold for discrimination and neither you nor the author of the article can insert one.
I guess you and I will have to agree to disagree.