In the U.S., the president isn't just head of government, such as a Prime Minister, but is also Head of State (I hesitate to say "like the Queen," but akin to a ceremonial state President in other countries). There it's a tension inherent in this hybrid role: the president must be a politician, but also a statesman who is above party politics. The President and the Presidency are national symbols. We have many national symbols. Mr. Trump deplores flag desecration. He needs to insure that the Presidency - as a national symbol similar to the flag - maintains requisite dignity. We might disagree with policies - that's politics - but we should not have to be ashamed of his demeanor. We should expect proprietary and dignity.
There are many people with whom I disagree on politics, but who have sterling characters - people with whom I disagree, but for whom I have deep respect, sometimes bordering on reverence. I want to be able to say that about a man who is to be president.