If you look at the way ISIL and its followers live, there is clearly a large cultural and sense of identity rift compared to the Western way of life.  And this is why they want to establish their own caliphate.  But no one seems to see that or want to recognize it.   You acknowledged this fact to a degree in your second last sentence.  However, it is not just traditional family values we are talking about.  It is the broader and harder to understand differences in societal culture and values.  You really have to ask yourself why Manchester's young women and children attending a music concert were such a target?