In June, Lawrence W. Reed of the Mackinac Center gave a speech to the Heritage Foundation on why conservatives seek to limit the size and scope of government (okay, some conservatives). He dances around the constitutionalist arguments, but doesn't really dwell long in that territory. His arguments focus mostly on common sense arguments, such as: except for "certain minimal, but critical functions", there's very little that government can do better than individuals, businesses and private organizations acting in voluntary association. And, you don't really want the government you think you want:
With regard to government, at the "core" of our core principles are these unassailable truths: Government has nothing to give anybody except what it first takes from somebody, and a government that is big enough to give you everything you want is big enough to take away everything you've got.
The entire speech is well worth the read.