Treason is no laughing matter.

Nonetheless, after President Donald Trump faced serious blowback for saying that Democratic members of Congress were not only un-American, but also treasonous for failing to stand and applaud some of his statements during last week's State of the Union address, a White House spokesman tried to wave away the criticism by claiming that Trump had been speaking "tongue in cheek."

Yeah, sure. That old chestnut again. Trump says something outrageous, completely out of bounds. People react. The White House dismisses the critics as failing to get the president's joke. Some of his defenders suggest it's not such a big deal, but just another case of Trump being Trump. And many more say nothing at all.

None of these responses is acceptable. To call one's political opponents treasonous for not standing and applauding wildly is the kind of thing one expects from some tinhorn dictator, not from the president of the United States of America.

Here was Trump, speaking on Monday at an event in Ohio that was ostensibly about the economy.

Of Democrats's failure to rise and applaud during sections of his address the previous week, he said: "[T]hey were like death and un-American. Un-American. Somebody said 'treasonous.' I mean, yeah, I guess, why not? Can we call that treason? Why not? I mean, they certainly didn't seem to love our country very much."

On the contrary. Dissent, especially in the face of someone who frequently behaves more like a dictator than as our constitutionally empowered chief executive, is a most-patriotic act.

What a president says matters. At least it is supposed to. And used to.

Here's how the U.S. Constitution, in Article III, Section 3, defines treason:

"Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort."

Trump, of course, doesn't know this, or doesn't care. Or both.

The country, and the world, has grown accustomed to the daily foolishness that passes Trump's lips or that comes off his Twitter feed. Most people can just roll their eyes, shake their heads, perhaps wonder how we've sunk so low -- and then move on, knowing full well that our nation's chief executive will spew a fresh bit of nonsense the next day. But Trump's statement on Monday was different. He crossed another line.

And Republicans in Congress again failed to step up. Does House Speaker Paul Ryan, R-Wis., think it OK for the president to talk so loosely of treason? If not, why did the speaker yet again fail to pipe up? How about Senate Majority Leader Mitch McConnell, R-Ky.?

It's bad enough having a president who routinely acts and speaks so carelessly, whose behavior is frequently so wildly out of bounds. What's even sadder is watching the GOP leadership, and the party rank and file, just go along for the miserable, dangerous ride.