When you have a war on your hands, isn't it ridiculous to ask "Are there no good Muslims?".
Yes, it is. 'Cause the war-time answer is "Good Muslims - in good coffins, bad Muslims in lousy ones..."
But seriously, the question isn't new, they asked it about Germans during the WWII. The answer was "Let's win, then we'll see".
In 1953, G C Marshall received the Nobel Peace Prize for his European Recovery Program which helped the Germans to return to the family of Western democracies. The very same gentleman was sworn in as U.S. Army chief of staff on Sept 1, 1939 - the day when Germany attacked Poland beginning the World War II.
More to your doubts: was it possible to distinguish between "good" and "bad" Germans before the victory?