All a 'Moderate Muslim' needs to do to prove they are right is to show how these 'radicals' have misinterpreted their religion by showing how they (the moderate) actually follow Muhammad example precisely and how the written word backs their position up. Why is that only the radicals can do that, leaving the moderates to hand wave and accuse those asking them difficult questions of being racist/Islamophobic/intolerant/ignorant/etc...
Perhaps your friend could answer that without resorting to a smart putdown...