Agreed, but with a few provisos.

Turning a peaceful protest (march etc) violet is a big no no. If there is seen to be a risk of this, the popularist section will rapidly hemorrhage members. The radicals can use the events as cover/meeting new members, but not go hot on the march. The exception to this is if the government/police go violent. Defensive counter violence is then acceptable. The goal should be to get the "civilian" supporters (think families etc) clear. Then, it's down to them whether they bolt too, or play whack a mole with the police.

The other proviso is that the radical groups actions should be proportional. The IRA walked this line. When they set major bombs, they gave the authorities enough warning to clear the area of civilians. They were mostly aiming for property damage and disruption, not mass casualties. The times the IRA went past that line did severe damage to their reputation. They need to act to reinforce the position of the other 2 groups, not undermine it.