1. not all religions are the same
2. not all religious doctrine should be free from scrutiny
3. there is a useful division we can make between the political teachings of a religion and the religious teachings of that religion
In case you don't know about Scientology's Fair Game policy, here it is in a nutshell: It is a written doctrine of the Church of Scientology that enemies of Scientology are "fair game" and may be (in the words of the founder of Scientology, "deprived of property or injured by any means by any Scientologist without any discipline of the Scientologist. May be tricked, sued, lied to, or destroyed."
This policy has been carried out by the Church of Scientology many times, often destroying peoples' lives, and Scientology's criminal actions (and its written policies supporting those actions) have often been documented in court. You can read more about it at Wikipedia: Fair Game (Scientology). Also, you can find good information about it at the Scientology Critical Information Directory: Scientology's "Fair Game" Doctrine. And also check out the Suppressive Person Defense League: Scientology’s Suppressive Person Doctrine.
Islam has successfully gathered a cloak of protection around it, making it difficult to talk about this subject with many people. People don't have the same knee-jerk defense of Scientology, and yet many of Scientology's teachings are similar to Islam's. So learn something about Scientology, and when you meet resistance when talking about Islam, switch to talking about Scientology.
Once you've made some good points, come back around and make the same points about Islam. I think you'll find this a powerful new strategy.
Read more about using this idea here.