Which is also what Macron didn't give Trump with his handshake antics.
... clarify a bit? Not sure whose handshake antics you're talking about, exactly. Trump had plenty of room to maintain dignity with that particular incident, if you're talking about macron's response -- all trump had to do was
not start things off trying to be a power playing jackass, or at least offer due respect when he was met in kind. The lesson there was that not everyone is going to roll over when the guy tries to shit on them, more than anything about necessary cooperation.
Though the bit I'd add to the dilemma question is whether it
matters if trump can learn or not, because the lesson is an important one to be (seen) teaching even if the other side is refusing to learn. Even if the material calculations come out in favor of going supine for a few years and then fixing shit, the ethical/cultural/etc. ones might not, y'know? Becoming known as someone that's going to capitulate if the other actor evinces sufficiently bad behavior can end up... not exactly ideal, on fields both foreign and domestic. Demanding a modicum of respect from a stronger power is risky, but so is not. And accurate or not, there's going to be folks who decide the not is riskier.