To return to the initial question posed by AOG - from the headline, it appears that AOG regards the behaviour of these people as ingratitude.
What we should understand is that our nation is only an expanded version of our families.
We bring up our children, love them, support them, take care of them, educate them, and then they go off into the world as adults to live as they please, because that is the freedom we enjoy.
Nowhere does it say that bringing up a child gives you first dibs on their lifestyle, politics, behaviour, etc. That is not a part of the deal. If your children live differently than the way you do, or the way you would hope that they would do, then that is part of parenthood.
Raising children is not an investment in the control of the behaviour of them as adults.
if you extrapolate that argument to a national level, you cannot expect that refugees taken into the UK will automatically stand behind its belief systems and customes, expecially where concience dictates that joining an armed struggle is perceived as the correct action.
As far as telling a moderate Muslim from an extremist one - the chances are the same as a moderate or extremist Jew, or Christian, or Jeddi - outward signs are limited.