It's about there being a middle ground. Basically just saying, 'lol it's okay guys, he was just crackers' is stupid. Obviously people come out with that stuff because it a) might be the case, or b) to balance out the awful Islamophobes, or c) to try and show just how beautifully liberal and loving they are, or whatever else. But it's insane! Of course we should look any possible religious cause (or partial cause)... surely it should go without saying we can look at combating radicalisation, and so forth, without in any way saying Muslims are all awful. If he was a mental person who found Islam as a crutch, and then an excuse, or whatever... that doesn't mean we should just ignore the second part, it means we should look at how to stop similarly mental people being similarly radicalised, if there was a religious motivation behind the actions (which it seems there was, given the paraphernalia he took...)