re: Why aren't we shooting down NK's missles?

Not necessarily. I don't think our mindset is "it's okay as long as you're not aiming at anything of our concern." We've been as stern as we can be with our "no testing allowed" message. If we could shoot one out of the sky simply because they are testing, we would. The article does address the issue of not shooting one down because it wasn't going to hit anything, but that is more of an excuse than a reason at this point.