Repeating a charge that he has made on previous occasions, Bernie Sanders has called Donald Trump a shameless liar. That might seem unremarkable, since Trump is, demonstrably, just that. But I don’t think any other major US politician has come out and explicitly applied the l-word to Trump since he became president.

Predictably, at least one Washington journalist, Amber Phillips, has criticized Sanders for his bluntness—Sanders is “lowering the state of our political discourse” by speaking that way of the President of the United States. Phillips admits that Trump says things that are untrue, but it can’t be proved that he doesn’t believe them, so it’s wrong to call him a liar. Presumably, even a president who habitually spouts falsehoods must enjoy the benefit of the doubt about his veracity. But, as I have pointed out, while Trump may possibly believe some of the nonsense he spouts, he has made numerous statements that he had to know were false. So why should he enjoy any benefit of the doubt about the many other demonstrably false statements he makes? In any case, an allegation made without any concern for its supportability in fact (like the alleged millions of illegal voters last November) is the operational equivalent of a lie, and very nearly the moral equivalent.  So what if its maker has conned himself into believing it might be true? Would Phillips prefer that we call Trump a deceptive delusional fantasist? Would that more nearly uphold her high standards for political discourse?

Sanders’ response to Phillips was spot on. Not only did he defend himself, but he asserted that, while he believes in civil political discourse, it’s important to call Trump out as a liar. To do otherwise would tell the world that habitual lying is a new normal for the President of the United States:

What should a United States senator, or any citizen, do if the president is a liar? Does ignoring this reality benefit the American people? Do we make a bad situation worse by disrespecting the president of the United States? Or do we have an obligation to say that he is a liar to protect America’s standing in the world and people’s trust in our institutions?”

The point is: bluntly calling Trump a liar serves to uphold, rather than violate, prevailing norms of political discourse. The most important such norm, I would think, would be a basic respect for the truth. To ignore or euphemize Trump’s disdain for the truth contributes to legitimating mendacity as a more or less normal and acceptable feature of our discourse.

I would make the broader point that disrespecting Trump does not amount to disrespecting the presidency. On the contrary: Trump demeans the presidency practically every day with his puerile antics as well as with his lies. Expressing appropriate contempt for Trump is a way of saying that this is not normal or acceptable behavior in an occupant of the White House.

So, let’s hope that more of our politicians get into the habit of calling Trump the liar that he is. Until, that is, he stops lying. I don’t expect that to happen.