One of the costs of the Trump era is that all opinions become suspect because everything is seen through the prism of whether you are for or against the president. Criticism of Trump is regularly assumed by his supporters to be rooted in bad faith.

Our salesman-in-chief revels in his skill at covering up and deceiving. But charges of hypocrisy against those who question Trump extend to the substantive matters as well. It's thus important to take on two deeply flawed but predictable arguments that have been offered in defense of Trump's lovefest with North Korea's brutal dictator and the president's approach to negotiation.

The first is that because the United States has sometimes allied (and frequently negotiated) with dictators, chastising Trump for ignoring North Korea's loathsome human-rights record represents a double standard.

It's true that human rights have often taken second place behind calculations about national security based on realpolitik. The U.S., rightly, joined with Stalin to defeat Hitler because, between the two murderous regimes, Hitler's posed the imminent danger. During the Cold War, the U.S. at times supported the installation of right-wing dictatorships to foil the communists or to protect American businesses.

But our wrongful indifference to human rights in the past should not be used as an excuse to justify apologias for dictatorships in our time. Moreover, previous American presidents (including Barack Obama, both Bushes, and Nill Clinton) have managed to negotiate with unsavory adversaries without pretending they were embodiments of George Washington or Nelson Mandela.

Trump did not simply overlook the astonishing brutality of North Korea's regime. He heaped praise on Kim as someone "very open," "very honorable," "very smart," "very worthy," and "very talented" who "wants to do the right thing."

Most appallingly, Trump, fresh off nasty rebukes of the leader of friendly and democratic Canada, told ABC's George Stephanopoulos of Kim: "His country does love him. His people, you see the fervor." Yes, fear of a gulag can produce a lot of "fervor."

Sorry, Trump defenders, but this is obscene.

The second canard is that those who once expressed alarm over Trump's loose talk about nuclear war have no right to critique his diplomacy. Never mind that he made real concessions to North Korea — beginning with the legitimacy that the Singapore extravaganza conferred on Kim and Trump's decision to call off joint military exercises with South Korea — without winning anything concrete in return.

Trump himself tweeted out this line of thinking, asserting that "pundits & talking heads" who were "begging for conciliation and peace" were now saying "you shouldn't meet, do not meet."

But as usual, Trump was distorting what his critics were saying. True, we wondered why he gave Kim the meeting without extracting anything of substance in advance. Yet his harshest detractors were among those pleased that Trump was talking rather than brandishing "fire and fury." This just goes to show how low he has set the bar.

And that flimsy piece of paper Trump signed guaranteed absolutely nothing and contained far weaker promises than those wrung out of North Korea by earlier administrations — promises, by the way, that the "very honorable" regime broke.

On MSNBC's "Morning Joe" on Wednesday, Sen. Chris Murphy, D-Conn., summarized the case against Trump nicely: "We're not against diplomacy. We're just against bad diplomacy, and this was really bad diplomacy."

And deluded diplomacy as well. Consider that upon returning home, Trump tweeted that "There is no longer a Nuclear Threat from North Korea."

When the most optimistic scenario is that the president doesn't really believe what he's tweeting, we have ample reason to doubt his competence and his motivation. And, fortunately, we're not required to demonstrate our "fervor."

E.J. Dionne (ejdionne@washpost.com) is a columnist for The Washington Post.