The use of the word "sad" by the Trump supporters is intriguing. If I'm parsing it correctly, the people using the word have concluded that they have the morally correct position, but there's no use trying to explain themselves to those who don't "get it"
Furthermore the people using the word view themselves as compassionate, and in a lot of cases it's true. They are compassionate to a specific view of the American dream. They genuinely believe America was better at a perceived time when simply being white and a high school graduate was enough. Steady, simple work, belong to the union, things are good. Work a little while and buy a house, maybe a summer house and a boat, stay at home wife with a couple of kids. Responsibilities sure, but not hard ones.
Well, it's not like that in reality. In 2016, work is longer and harder, more challenging intellectually and technologically speaking. There's more demand for good paying jobs from people who have come from all over the world with degrees from good schools, advanced degrees in many cases. Those unwilling to work hard to compete in this environment, the lazy uneducated whites and their wives, look upon this reality with "sadness". They want their American dream, on their terms. And so a wall, and anti-immigration, and anti-trade sound like pretty appealing policies. Marry that up with "MAGA", and it the appeal makes sense on some pathetic level.
So when I see the word "sad" when used by the Trump supporter, it indicates to me they are deluded and don't deserve the time convincing otherwise, because their starting premise is that their position is morally superior, so there is no intellectual argument that would persuade their position.