Humans favour their own group – even when that group is an arbitrary label given them by experimenters. They like members of their group more, see them as superior, and behave more altruistically and forgivingly to them. The dominant explanation among social psychologists for this "group identity" is pride. People's "social identity" as a group member is part of their personal identity, and they support their group to shore up their own self-esteem.
I prefer the theory that group identity comes from fear. People stay close to their own group and support it, because they fear the other group. That in turn makes members of the other group afraid and pushes them closer together.
So far Western politicians have been responsible in differentiating between terrorists and peaceful Muslims. George Bush was adamant that the US was waging a war on terror, not on Islam.
Let us hope that this will last. But there is a lot of fear in France now, and a big potential audience for leaders who promise to keep the majority safe. The decline into mutual fear and hatred can be fast: when the situation gets dangerous, everyone is forced to seek protection from their own group's warlords and thugs.
I feel this change even in myself. I struggle to remain open-hearted. But a little voice within me starts whispering that perhaps the bigots are right, that Le Pen has a point, shouldn't we ban the headscarf, on feminist grounds of course... How many people in France are going through the same mental process?