Muslims give The most common description about Islam that it is a Misunderstood religion. They say terrorists misunderstand Islam. Here is one case where a police could not convince the terrorist that he has misunderstood Islam. 
The earliest usage of the "terrorists misunderstand Islam" dialogue which we can recall is when 9/11 happened. That's more than 16 years ago. Terrorists should not continue to misunderstand Islam after so many years. Then why does terrorism continue? It is because terrorists understand Islam correctly and practice every letter of it.