A man enjoys religious liberty when he possesses the free right of worshipping God according to the dictates of a right conscience, and of practicing a form of religion most in accordance with his duties to God. Every act infringing on his freedom of conscience is justly styled religious intolerance. This religious liberty is the true right of every man because it corresponds with a most certain duty which God has put upon him.

A man enjoys civil liberty when he is exempt from the arbitrary will of others, and when he is governed by equitable laws established for the general welfare of society. So long as, in common with his fellow citizens, he observes the laws of the state, any exceptional restraint imposed upon him, in the exercise of his rights as a citizen, would be an infringement on his civil liberty.

I here assert the proposition, which I hope to confirm by historical evidence, that the Catholic Church has always been the zealous promoter of religious and civil liberty; and that whenever any encroachments on these sacred privileges of man were perpetrated by professing members of the Catholic faith, these wrongs, far from being sanctioned by the Church, were committed in palpable violation of her authority.

Her doctrine is, that as man by his own free will fell from grace, so of his own free will must he return to grace. Conversion and coercion are two terms that can never be reconciled. It has ever been a cardinal maxim, inculcated by sovereign Pontiffs and other Prelates, that no violence or undue influence should be exercised by Christian princes or missionaries in their efforts to convert souls to the faith of Jesus Christ.
http://www.tanbooks.com/doct/tradition_faith.htm