The colonists already had 'that freedom' - meaning the power to establish their own church. The colonists had the biggest 'Pope day' they ever had in 1774 - in which they paraded around and hanged an effigy of the Pope. Alexander Hamilton warned that the Quebec Act would attract Catholics from throughout Europe to immigrate to the territory and eventually destroy America. The Continental Congress wrote a statement to the people of Britain stating the following:
http://en.wikisource.org/wiki/Address_to_the_People_of_Great_Britain
"Nor can we suppress our astonishment that a British Parliament should ever consent to establish in that country a religion that has deluged your island in blood, and dispersed impiety, bigotry, persecution, murder, and rebellion through every part of the world.
This being a state of facts, let us beseech you to consider to what end they lead. Admit that the Ministry, by the powers of Britain and the aid of our Roman Catholic neighbors, should be able to carry the point of taxation, and reduce us to a state of perfect humiliation and slavery. Such an enterprise would doubtless make some addition to your national debt which already presses down your liberties and fills you with pensioners and placement We presume, also, that your commerce will somewhat be diminished. However, suppose you should prove victorious, in what condition will you then be? What advantages or what laurels will you reap from such a conquest ? May not a Ministry with the same armies enslave you? It may be said you will cease to pay them; but remember, the taxes from America, the wealth, and we may add the men, and particularly the Roman Catholics of this vast continent, will then be in the power of your enemies; nor will you have any reason to expect that after making slaves of us, many among us should refuse to assist in reducing you to the same abject state."
This is also worth reading.
http://blog.beliefnet.com/stevenwaldman/2008/04/how-anticatholicism-helped-fue.html
http://www.baptistpillar.com/bd0122.htm