"We can't let this threat go without response."
No you keep your mouth shut. It's clear they are posturing. One nuke headed our way and they know they'll be governing a sheet of glass.
Consider this. Whereas, when the USSR glowered over Europe with their SS-20s, which are an entirely different animal than ICBMs, due to the shorter distance and shorter flight times, we responded with Pershing-2s slated for Europe, nuclear armed ground launched cruise missiles actually deployed in Europe, and our SDI plan, all the while vastly increasing our conventional punch. Now, with the PRC similarly glowering with DF-21s over SE Asia, Japan, Taiwan and other nearby countries, all of them with NO nuclear weapons, we are not responding. To compare with the past European situation, instead of taking a Ronald Reagan approach currently we are taking a Jimmy Carter approach. Where will it lead?
What response would you suggest?