Every single-issue person is a purist, even if that single issue is the Constitution. Purists have a holier than thou self-image. That makes purists vociferous and bold in action. They look down in total amazement upon others that do not share their passion.
Why is purity about the Constitution any different than purity about any of the other major issues like Guns or Abortion or Economy? I don't think there is a difference. No, but constitution is a level higher and encompasses all the other issues, say the constitutional purists. Well, yes, but only from a legal standpoint. There is a custom and tradition part of life that predates laws and can not be ignored.
More under the fold ...
The people of the United States did not suddenly come into existence with the adoption of the Constitution. They had their own ways of living and organizing but chose to form a democratic union because they felt this might be a worthwhile experiment and better than the contemporary system at the time. Just because this experiment has survived for over two centuries, albeit with significant challenges, does not mean the experiment is perfect. If longevity alone means success, then almost every religion is a more successful organizing principle than the US Constitution.
Ok. Another close relative of the purity phenomenon is perfectionism or idealism. Any recovering idealist or perfectionist knows it is not easy to get out of it. It is kinda about individual moral development. One needs to be able to keep competing thoughts and ideas in one's head and still be able to function.
So here is the point. If anyone is emotionally and viscerably uncomfortable with the FISA issue or with any particular position taken by one's favorite politician on it, try to first become aware of the possibility of being a perfectionist. Everything passes and time heals, but if one works hard on oneself it is possible to gain a broader perspective and become a more developed person.