There has been a lot of commentary over the last few years - decades, really - about the problem with Muslims who are not violent or criminal in themselves, but still provide cover for and excuses for those who are dangerous extremists. I suspect there is a continuum, or more properly, a mix of motives. Some are secret sympathisers only too happy to do their bit. Others may be afraid of retribution against themselves or their families. Most likely of all would be those who know that the extremists' level of violence and hatred are wrong, but excuse it as tit-for-tat of things done against the Muslim community. Or, given the way that rhetoric runs, what they believe would happen to their community if they let their guard down for a moment.
I offer these guesses because we have seen this before in America. Many times. How is this different from Italians covering for the Mafia, which was true within living memory and still has some residue? In Boston and Chicago, organised crime was often Irish - Whitey Bulger was a veteran of the Killeen-Mullen war and ran free for many years, even though plenty of people knew where he was; in New York there was a strong Jewish and later Puerto Rican element to organised crime. The recent book Ghettoside by an LAPD detective describes how difficult it is to get witnesses to come forward in Hispanic and especially black communities because they are so fearful.
Colonists and Indians likely covered for their own. It is the natural way of all tribes.
I see one difference, but I am not sure it is large in the long run. The other groups I mentioned were covering for criminals - guys trying to make an illegal buck - rather than people who wanted to change the government and social order. This would be similar to Basques or IRA, perhaps. Is it different?