Trump has something of a point in these trade disputes.
At the core, there’s a game of “chicken” being played. In principle everyone wants fair trade rules, but the issue is extremely complex and there’s a lot of room for ambiguity, and naturally everyone tends to see what’s fair in line with what benefits them. And the problem is that if you make clear upfront that you value free trade and fear trade wars so much that you will never under any circumstances get involved in a trade war, then the guys on the other side of the table have that much less incentive to agree to terms favorable to you and all the more incentive to hold out for an agreement more along their lines. Trump’s position is that the US is essentially in this position. I suspect there’s something to it.
That said, there’s a lot of room between having “something of a point” and being correct about the details and right about the strategy. I’m not very up on the nitty-gritty details of many of these trade issues, but I don’t have a lot of confidence that Trump is either, to put it mildly.