I was thinking along those lines earlier today. Whenever some Muslim acts like a Muslim there is always someone to say that they do not represent true Islam. Then what is Islam? You hear of nothing but evil coming from them and being of them.
That’s when you say to them: They murdered and raped non-Muslims. Didn’t Mohammed Murder and rape non-Muslims? Etc. Let them know you know what real Islam is and that those real Muslims should be taken seriously because they know they are following the behavioral guidelines set down by Mohammed and A-llah.