Let's use an anology you may be able to understand. Let's say you're a parent and you have a child throwing a temper tantrum. Just because you can is it okay to beat the child as you would an adult attacker? How about teaching the child a lesson by leaving it at the store so they can find their own way home to learn a lesson?
*Laughs* Jesus. Well, that's sure an example. A totally bat**** crazy one, but an example all the same.
Temper-tantrum-throwing toddlers can't blow up half of Asia, and aren't going around throwing even weaker children in gulags to starve for a decade.
Yes, North Korea should be treated cautiously, and not hold their abilities to the same standards as, say, China or Russia. They're still a huge threat, and you do still have expectations for them. No nation on earth isn't going to have second thoughts about meeting with a foreign adversary for high-stakes talks when things have had an uptick in aggression to the point of singling out the VP & Sec State with mudslinging.
The same reason you wouldn't want Trump & Kim to meet earlier on when all the "dotard" and "little rocket man" stuff was flying around. It's just not a good time to bridge gaps. Take a breath, wait until things calm down, and pursue something then.
So, basically, they probably could have gone ahead and tried to make this work. Maybe even should have. But a delay also isn't some indefensible thing under the circumstances.
You'll be pleased to know they've got even more conciliatory with each other today and yesterday, both sides publically wanting to make something work whether it's in June or sometime after. The sky's not falling.