Trade is an issue not because free trade is bad.
Trade is an issue because free trade fails to compensate for the differing burdens that items 1 and 2 place on US companies vs. foreign companies.
The cost of managing distant factories and moving factories was an obstacle that allowed disparities in items 1 and 2 to arise without destructive effect. But, with the ever increasing ease of international transfer of factories (item 3), items 1 and 2 are becoming a big issue now.
Because we can't roll back the clock on item 3 (ease of transfer), Trump proposes to directly reduce one disparity (item 2, regulations) directly, and to mitigate the effect of another disparity (item 1, compensation) indirectly by directly addressing Item 4 (trade). Item 5 (robots) will happen globally no matter what.
Now, I'm hesitant to engage in a trade war, but I think that Trumps point is that we are already in a trade war because of disparities in compensation and regulations. He proposes two solutions, and we can argue about the merits of his solutions. But, Hillary merely proposes ignoring the problem.