Yep, you got it. The joke is: "when US claimed you have wmd, you better actually have it"... NK has been behaving quite bad comparing to some other countries

Yep, you got it. The joke is: "when US claimed you have wmd, you better actually have it"... NK has been behaving quite bad comparing to some other countries that got US invasion. The reason that they were not invaded, is mostly that they indeed have the stuff that can scare away US.