I think more effort should be done by the countries fighting terrorist organizations to save the members who are younger and more vulnerable. They are easily manipulated by the older to do the dirty work and wear their kamakaze vests to destroy villages. The younger are easier to recruit too.
Children should be rescued from extremist terrorist organizations to keep from being brainwashed because they are innocent beings, and terrorist organizations have demonstrated they cannot care for children. Additionally, if the terrorist organizations are committing violent crimes, rescuing the children may prevent them from facing violence and reduce the spead of influence and in the long term, reduce terrorism.
No, children should not be rescued from extremist terrorist organizations to keep from being brainwashed, because it's a slippery slope into removing children from families that teach children unpopular things. As long as children are not being physically abused or neglected, a parent has a right to teach her child to grow up to hate, as shameful as it is. The government can't be the thought police, because the government shouldn't be telling people what to think.
Brainwashing is the least of the problems that children who are raised in extreme terrorist organization face. This children face an almost certain death when they grow up, either by those fighting terrorism or by a suicide attempt. I think they should be rescued from these terrorist organizations, but to save their lives.