Another excellent post from David Kerrigan here.
It was Thomas Helwys, an English General Baptist who came from the East Midlands who famously wrote:
‘For our lord the king is but an earthly king, and he has no authority as a king but in earthly causes. And if the king’s people be obedient and true subjects, obeying all human laws made by the king, our lord the king can require no more. For men’s religion to God is between God and themselves. The king shall not answer for it. Neither may the king be judge between God and man. Let them be heretics, Turks, Jews, or whatsoever, it appertains not to the earthly power to punish them in the least measure’. (Helwys, Mystery of Iniquity)
Our claim to be 'for' freedom of religion does not always work itself out in daily living, and of course it is no simple 'anything goes' viewpoint. But it's a good principle.
Go and read David's article, which cites some helpful material by Brian Haymes too.