When the legitimacy of a government is based upon religion, then any challenge of the religion is treason against the rulers. This is the reason behind the Inquisition, the various Catholic/Protestant conflicts, and the attitude of Islamic rulers towards heresy.
When the legitimacy of Western governments stopped being based on religion, religious wars abated.
You are very mistaken. The principles of western democracy are based upon Christianity and every major war of the 20th century and the wars of the last decade have ultimately religious wars between Christianity and the godless.
Peace be with you.