There is a difference between saying that "All Muslims are terrorists" and saying "All terrorists are Muslims".
Both statements are false. There are LTTE terrorists in Srilanka, IRA terrorists in Northern Ireland, and Basque terrorists in Spain. And there are many Muslims who are not terrorists.
But Islamic terrorism is unique, because it is supported by Islamic doctrine as per Quran, and the acts of the prophet himself, as recorded in the Hadiths. So Islam is the problem. Understand that, and work on making Muslims understand it too.