Simple. If it's a peaceful demonstration, there is no need for force. If it is not peaceful, they are breaking the law, and the police have the obligation to start making arrests, and by force if the violent protesters will not comply peacefully.
This question creates a false dichotomy. It's not religion that is the problem. It's Islam. If the world didn't have Islam, the world would be a better place. If the world did not have Budhism, Hinduism, Christianity, Judaism, etc, it would be a worse place. Hitler, Stalin, etc showed what an anti religion viewpoint does.