The Trumptardians are screaming for this war to happen. Of course, none of them have to actually go. They don't understand the on the ground carnage that's going to take place. Like someone else said, Seoul will get flattened. There's also the small matter that NK could conceivably launch a nuke at SK, Japan, or even more likely, one on the battlefield. In either of those three instances, longstanding U.S. military doctrine is to respond not just in kind, but with X times the force.
Now, say we nuke Pyongyang. How far is that from the Chinese border? I'll speculate and say that it's the distance from the southernmost section of California to Ensenada in Mexico (about 86 miles). So how would 'Merica feel if for example, Putin dropped a nuke on Ensenada? There isn't big enough hypothetical diaper to contain the mammoth sized shit America would explode out of its collective ass over that. But China's gonna be all, "Hey, it's cool yo." Right.
Putting aside the nuke thing for a moment, the conventional war would be like something that hasn't happened since the first Korean war. Assuming the NK military doesn't fold up like the Iraqis did in the first Gulf War, there will be tens of thousands of American soldiers dead. The logistics of having to reinforce them would come at an enormous cost.
Of course, this doesn't take into account the question of what in the fucking world does South Korea think of all this? Sure, we need to teach the little fat kid in North Korea a lesson, but maybe we should think about the welfare of the nation that a good portion of this war is going to happen on. But conservatives don't really think of Asians, Arabs, or any non-white individual outside of the U.S. as living, breathing humans. After all, the little fat kid's been disrespecting us and for that he needs to pay.
The only solid counterargument to be made here is that the fat kid would still be a joke if he didn't have nukes. But he does. And he's threatened to nuke SK, Japan, and the U.S. And no one wants to be sitting in the White House if that happens when it could've been prevented. And any sane person certainly doesn't want Trump there if/when it happens.
Let's face it though, diplomacy hasn't worked because of China's titty-mama role in all of this. Rather than replace the NK regime with a sane one, they support it. And it's not like this NK regime is all that different from the the two that came before it. It's just as weird, corrupt, and belligerent, except now it has nukes.
Unfortunately, we don't have the brainpower at the levels of government that are needed to fix this.