Supporting a leader doesn’t require supporting all their behavior. Yes, POTUS Trump is on Twitter returning evil for evil, admittedly being an unbecoming counter puncher.
But the Bible has long taught that He uses imperfect vessels to accomplish his word, and that God’s people should still them. As an example, Daniel was carried away and forced to serve the destroyer of his country, Nebuchadnezzar king of Babylon. That king did horrible things like had a harem, murdered thousands and was extremely arrogant. Yet, Daniel understood the king played a role in God’s plan. His language was still respectful despite the king’s sins. When Nebuchadnezzar had a dream prophesying his own humbling demise by being turned into someone like an animal of the field Daniel did not rejoice, but instead said, "My lord, if only the dream applied to those who hate you, and its interpretation to your adversaries! "(Daniel 4:19).
He was practicing a verse from the law which was later repeated by the apostle Paul for us. You shall not curse God, nor curse a ruler of your people (Exodus 22:28).
Therefore, POTUS Trump’s alleged moral sins, with most in the past, are not prohibiting Christian support. We already knew he was a sinner and are more concerned about his behavior now that could negatively affect the defense, economics and judiciary.
What they currently preach is much more important than what they’ve practiced. King David illustrates this. He lusted after Uriah’s wife, impregnated her and tried to cover it up by having Uriah killed. Yet, even though in God’s theocracy of Israel, God did not remove him from being king. However, make no mistake, if he would have lauded his sinful behavior and tried to teach it to Israel, he would have been destroyed.
We must understand we live in a democratic republic not a theocracy. Therefore requiring religious piety for the POTUS is unnecessary. However, if POTUS Trump tried to preach his immoral behavior as good for all Americans then you would see Christian support plummet. He’s not the pastor in chief, but commander in chief.
Christians don’t worry about their families following his past or present example. We have Christ for that. We want him to protect the country through a strong military, having proper judges installed and evil doers punished. After all, how much we can expect from a man who in a speech said Two Corinthians, versus Second Corinthians?
Christians should be honoring the POTUS. Peter plainly states to honor the king (1 Peter 2:17). This doesn’t mean supporting every decision by a POTUS. It does mean the Christian should refrain from mocking, name calling, or any other dishonor. That’s America’s way, but not the Bible’s. To not give a general honoring to the leaders, is to not give honor to God (Romans 13:1-7). Since Christians were commanded to do that in the time of emperors like Caligula and Nero (whose behavior makes POTUS Trump’s look saintly), then the Christians of today should honor the president.