Notes:

Obviously, what happened in France was a tragedy. The people who did this are monsters who need to be brought to justice and should punished to the fullest extent of the law.
That said, I want to criticise all those who will use this as an excuse to declare that all Muslims need to be eradicated from the face of the Earth. Islam is not the problem here.
The problem is that the West has been at war with predominantly Islamic countries for nearly over a decade now. Cities have been levelled, civilians have been killed, and lives have been forever altered.
The rise of ISIS and other extremist groups is a response to this seemingly never-ending conflict. These groups draw their recruits from those who, for the most part, have never even heard of 9/11 and do not know why the West invaded them in the first place – all they see is foreign country attacking them and killing their families.
A lot of ISIS recruits join because they believe it is the only way to defend their country and families from the invaders.
Now, obviously there are ISIS members who legitimately want to destroy the West because of their twisted ideology. But if the West had never gone to war in the Middle-East, I doubt these types of groups would ever have become as big as they had.