The LORD says:
I will not relent from punishing Moab
for three crimes, even four,
[And what are these heinous crimes?]
because he burned the bones
of the king of Edom to lime. (Amos 2:1)
And that's where the list of the sins of Moab ends... Odd. Now, If Amos is about justice, what does God's punishment for the bones burned to lime tell us about God's view of justice? If justice is in part, as Augustine says, giving each person what is due to him or her, how is burning the bones of a king a failure to do right?
Primarily, I think it shows dishonor to a king: an individual who is appointed by God to rule. God tells us clearly that a ruler deserves honor or respect. Peter says "honor the emperor" in 1 Pet 2:17, meaning either Nero or Domitian (depending on dates)! Paul says the same in Rom 13:1–7. It is part of Christian ethics to honor those in civil authority over us.
You can say what you will about the ethics of a Trump presidency, but he pales in comparison with dictators like Nero or Domitian. And yet, Jesus and apostles alike all told us to give honor to whom honor is due. A president is one such person. If you believe in justice, God includes honoring rulers—even foreign ones (Moab vs. Edom)—in the scope of what it means to do justice. We don't get to pick and choose the parts of justice we like and don't like. Our part as created beings is to do justice, love mercy, and walk humbly with God.
With that said, honor is different from support or agreement. You can oppose the agendas the president pursues while honoring him as a person and a leader; as a citizen of a democratic republic, you can oppose him at the ballot box while still giving him honor; you can stand up for the poor and mistreated even when the government does not while still showing honor. You need only read early church history to find examples (and the cost) of how this may be done. We far too often conflate disrespect with opposition. We are commanded, brothers and sisters, to show honor to kings and citizens alike as we pursue justice for those "the system" has given disrespect, dishonor, and injustice. Overcome evil with good, put hate to shame with love.