With all due respect, these people are explaining why the people of Quebec thought the way they did. The Quebecois of 1812 weren't aware that Andrew Jackson would appoint a Catholic to the Supreme Court in 1836; they didn't know that the First Amendment, which had been in place less than a generation, wasn't going to be revoked or would offer religious tolerance to anything other than Protestant worshippers. They did, on the other hand, know how the colonists had reacted against the 1774 Quebec act's tolerance of Catholicism:
10. That the late act of parliament for establishing the Roman Catholic religion and the French laws in that extensive country, now called Canada, is dangerous in an extreme degree to the Protestant religion and to the civil rights and liberties of all America; and, therefore, as men and Protestant Christians, we are indispensubly obliged to take all proper measures for our security. (Suffolk Resolves, 1774).
As has been stated many times in this thread- though you and a few others don't seem to appreciate the subtleties of the argument- the Quebecois were offered a choice between an existing government which had shown no intention of interfering with their religion and an unknown quantity, which had previously inveighed against their beliefs and whose supposed religious tolerance was not guaranteed to work on their behalf in practice.