President Donald Trump doesn't follow that rule. Asked about the passing of legendary journalist Cokie Roberts on Tuesday, here's what Trump said (in part):

"I never met her. She never treated me nicely. But I would like to wish her family well. She was a professional, and I respect professionals."

So, yeah.

The first words out of his mouth when asked about someone's death was a) never met her and b) "she never treated me nicely." Me, Me, Me, Me, Me Me.

While all politicians -- and all people -- tend to see things through a how-does-this-impact-me lens, most of us understand that turning everything, especially someone else's death, into a conversation about ourselves is hugely selfish and narcissistic. It also reeks of a lack of empathy, an inability to step outside yourself and into another person's shoes for even a minute.

That Trump's first instinct when asked about the death of a prominent journalist would be to make it about himself and then use it as a piece of ammo in his long-running fight with the news media is, even for this president, a remarkable thing. And by remarkable, I mean revealing. Revealing in that it makes clear -- and, if you have been paying attention to the presidency it might well already be crystal clear to you -- that Trump is simply unconcerned about anyone who isn't him. He doesn't view the presidency as a position of moral leadership. He just does and says what he wants, when he wants.

That rejection of moral leadership -- of taking the high road, of understanding that you don't need to say everything you think -- is what makes Trump truly radical vis a vis the other men who have held the office of president. They tried -- and sometimes failed, but always tried -- to do what they believed to be the right thing, even if it wasn't what they wanted to do. Trump makes no attempt to do so. None.

You can argue that what Trump says about a deceased journalist isn't that big a deal -- especially when compared to some of the other things he has said and done as president. I get that. But, it reveals something far deeper -- and darker -- about Trump.

Someone who is incapable of expressing empathy -- or even of not saying something bad! -- about a dead person is someone who is so self-focused as to be largely (if not totally) blind to the world around him. That's a problem for any person. It's a massive problem -- and should be a huge area of concern -- when the person we are talking about is the president of the United States.

None of this, of course, means that Trump can't or won't win in 2020. After all, he won in 2016 even while badly losing voters who said a candidate who "cares about me" was their biggest priority. Voting for Trump in 2016 was about choosing a radical change agent and it's indisputable that he's been that.

But, the assumption that all change is good change is a mistaken one. Whether Trump wins or loses next November, his lack of empathy and presidency devoid of moral leadership will have fundamentally altered the way in which the presidency is conceived in at least some circles in the country. And not in a good way.