Are all Muslims really sure that Islam is a religion of peace?

After reading parts of the Koran which states that Muslims should kill all who are not one of them, I never believed that Muslims or Islam is a religion of peace. I do know some very nice Muslims, but they for the most part do not follow the whole religion, just bits and pieces of it. O'Reilly was correct when on the view he stated Muslims when he referred to terrorists. They are what they are.