Adam Smith's The Wealth of Nations could be considered the founding document of modern capitalism, and Smith was a strong advocate of free trade, but even he noted some exceptions. Aside from the parochial interests noted above, there are other objections to completely free trade. More stuff for everybody is nice, but anyone with a knowledge of history or biology knows that you need more than that to survive. Smith made an exception for items necessary for national security and everyone since has agreed.
Survival doesn't just require food, it also requires escaping predation. For the past several thousand years, at least, the predator most dangerous to humans was other humans. This fact shaped and continues to shape our culture and institutions. Direct competition between families, hunting bands, tribes, cities, and nations is one of the means of predation, so every nation has needed to defend its survival. Ever since the invention of agriculture, groups and nations needed internal methods for dealing with excess population. Social hierarchies were the fundamental mechanism for dealing with the Malthusian crisis agriculture produced. The upper classes might flourish, but one critical job for the poor was starvation.
Thomas Malthus was only ten when Wealth was published, but Smith anticipated him in some key respects - see, for example, his comments comparing the reproductive fecundity and terrible survival rate of poor Scottish highlanders with the lower fecundity and higher survival of the wealthy.
Malthus no longer rules the developed world, and much of the world is stepping back from rapid population growth, so there is hope for a world in which free trade truly could flourish, but human instincts haven't changed, which means that many people still find destroying the other preferable to prosperity for all. In that respect Trump is something of a throwback.