In America, many Protestants tend to distrust Catholics and Mormons. Whenever a Catholic runs against a Protestant in an election, many times the Protestant runs a "Pope-Baiting" campaign, and it has worked many times (in fact, the reason for the Democrats losing in 2008 could be traced to the VP candidate's Catholicism). As far as Mormons are concerned, while they are distrusted because of their small numbers most prejudice is centered in the Rocky Mountain states. Violence was particularly bad in the 1970s and 1980s, with the rise of the Protestant Militia movement and the Mormon and Catholic groups rising in response (most groups were self-defense in origin, though they were a few nutters who wanted to convert all of America to their branch), yet their popularity began to wane following the passage of the Militia Act in 1986, which led to a huge crackdown on such groups.
However, could this sectarianism become a fringe ideology? If so, how?