The question is NOT should Trump have walked away, but WHY was he there in the first place...Presidents who know what they are doing do not show up at initial meetings - their staff works out the details and they show up for the photo op - signing an agreement, not walking away empty-handed.
Ironically, perhaps, DJT ended his Hanoi road show shortly after Michael Cohen's testimony yesterday ended - a losing day all around for the self-proclaimed "great negotiator".