Honestly, I think that Jesus of Nazareth had it right on his 'render unto Caeser...' bit. From that it's clear why the idea of separatiing thee political arena from the religious one ould arise in Christian Europe. And it's just a good idea for everyone involved, unless they just want to crush everyone that doesn't share their philosophical conclusions.
"The reason things will never get better is because people keep electing these rich cocksuckers who don't give a shit about you."
-George Carlin
-George Carlin