Well, it all started off from Adam and Eve, Adam sinned (he banged her big time) - so our existence is from a sin, no human can be clean of sins, but then there are some who accept that they sinned and try to correct it by not doing the same sin again, others carry on living. We believe God is mercy full, no matter what sins or wrong doing you can always go back to hime and he will forgive you.
As for "cleaning yourself first" if I am a priest in the eyes of community but behind closed doors I am pedophile, how can I preach and be holy ? Same goes for Muslims, if they grow beard and talk Islam but kill innocent people, how can you trust them to show you 'the way'. For that reason alone, one should understand religion and follow it truly before judging someone else or preach. It's very easy to pick and chose what suits one's needs, with religion. I have
Known people who think the same way like you (Muslims) but that doesn't make them right or they don't represent Islam in any way or shape. It's just they think they are superior to other humans/Muslims because the have beard and talk crap.. In other case some Christian dude talking crap about holy church etc..
As for 'ISIS' well clearly you dismiss all other religions and believes, there is no middle ground with you or your arguments. It's your religion or nothing. If you were living in third world country and there is a chance for you to get armed and fight for Christianity, to save the holy church, won't you do it ? If that's the only option you have.