|Oregon protesters during the standoff (Source)|
Completely separate from this (and they must be walled off) are the militant or protest groups for the movement. Some of these will organize quasi-legal methods of protests: marches, sit-ins, strikes, etc. The umbrella organization may show up to show support of protesters, but shouldn't be connected to planning or organizing the protests.
A movement may (but not necessarily) be supported by radical militant groups: those responsible for clearly criminal acts such as illegally gathering intelligence, intimidating witnesses, raising funds through theft or robbery, perhaps even engaging in acts of terror. The umbrella organization may appear to be sympathetic to the causes or plight of the radical militants, but must never publicly be supportive of the methods, and never associated with funding or organizing such groups (although, in reality, the umbrella organization, or its leaders, are probably doing both). The membership of the radical or militant groups must be kept secret; their plans must be kept secret.
Communication between the umbrella organization and the militant group(s), and within the militant group(s), must be limited and secure. Plausible deniability must be maintained at all times. Again, I would refer you to the Lizard Farmer's article entitled "How They Hunt."
A couple of examples. CAIR probably seeks the imposition of sharia in the United States, but its message is a more palatable "the U.S. shouldn't discriminate against Muslims." Something that makes most people feel fuzzy and warm because no one wants to be called a bigot. Of course, the way to not discriminate against Muslims is to let them have their Mosques, the public calls to prayer over loudspeakers, their own holidays, getting rid of Christian Holidays, limit speech that is critical of Islam or Mohammad, their own courts, and so on--as we advance step by step toward the unstated goal of sharia.
"Black Lives Matter" appears to have a goal of setting up quasi-independent reservations for blacks (actually, fiefdoms for black politicians, but lets not quibble about semantics). Its public message is that police shoot too many "innocent" black youth. The means of correcting this problem, though, is granting more political control to blacks, thus advancing the unstated goals of the group.
However, if a radical group intends to undertake an act of violence, it needs to be one that also advances the message or movement rather than violence for violence sake. This requires a great deal of discipline, and is why most terrorist groups are ineffective. The goal of violence in advancing a movement is to either alienate the population from the government, or to draw the population to the movement. In either case, though, the movement cannot come across as weak.
The former goal is generally advanced by acts that show that the government is powerless or incompetent, or by prompting a heavy-handed reaction from the government that reduces its legitimacy. The formation and implementation of the TSA is a great example of government action that hurts government legitimacy because it is incompetent, and treats all members of the public as potential terrorists.
The second goal of drawing the population to the movement is generally accomplished when the movement is seen as protecting the population or providing services that the government cannot or will not. Mao used this quite effectively in winning over the support of peasants by protecting them from bandits, warlords, and tax collectors--all activities requiring the exercise of force--and providing health and education services. This second goal requires a close cooperation between the central movement and the militants, which is why it may be more difficult to put into practice. Nevertheless, it is probably more effective than simply attempting to alienate the people from the government.
The Oregon standoff was ineffective in its show of force because the standoff was essentially a sit-in, to which the members brought guns. They did not use the guns (so why they brought them, I don't know). I can't think of any situation where the members of the standoff could have used force to make the government appear ineffective. By bringing firearms, the members of the standoff opened the door for the government to use force (including lethal force) that would not have been condoned if the members had simply chained themselves to a gate or sat in the middle of the BLM headquarters chanting protests or holding up signs. Thus, rather than make the government's use of force appear to be excessive, it legitimized the government's use of force. Moreover, because the members involved in the stand-off ultimately did not resort to violence, but seemingly threatening it, it made the group appear weak and ineffectual.