Any conflict inevitably consigns many thousands, possibly tens of thousands, to an early grave. In particular the local countries won't come out of it well. It's surely not possible to strike North Korea in a way that knocks out everything they can use to damage their neighbours or assailants, so that's a great deal to ask of South Korea in particular to lay their country on the line.
That's not to say I don't agree with you about the principle. But what's to be done? A direct conflict with North Korea will be costly to both sides in terms of human life, and even while victory is certain the price will be high. As long as that can be avoided, it should be.
A missile that threatens to cause damage but ultimately splashes harmlessly into the sea is just about on the edge of tolerable. I still feel that Kim Jong-Un knows that starting an actual conflict is suicidal, so has no intentions of doing so, but wishes to continue showing his strength both to his people and to his enemies. It's a large-scale equivalent of "warning shots", and I think he's likely to stick to that. And as long as he's only "warning", then has he gone far enough to justify starting that deadly conflict? Possibly, but perhaps it is after all better to continue squeezing the country economically, or pursuing diplomatic approaches.
I'm no friend of Kim Jong-Un, but I'm no fan of starting World War Three either.