The reason the left ignores the Constitution (when it doesn't suit their purposes) is that they believe they, being modern day thinkers with more information than the founders, know better than those that wrote such restrictions on their behaviors.
As you said, though, two can play at that game.
"The founders couldn't have known that the educational system would become so corrupt that the majority would prefer communism. So, since we know better, given the information we have now, we are fully justified in not funding the government".
PS - you can do your part in not funding the gov't by jumping through a few hoops and legally reducing your taxes by about half, if you find out how.
I believe it is possible to get it down to Zero!