This eventually gets down to hypocrisy, such as kill the heathens; just bypass a step. Islam needs to modernize. There are plenty of modernized muslims out there of course. But, holy war and extremist religious people need to get shed from any religion, and then eventually, religion itself can be shed.
So what is offense? One thing is when people tell me i'm going to go to hell. I tell people who tell me i am going to hell quite directly to **** off. Part of the attack happens because anybody that knows me knows that i denounce religion even though i believe in god and read the bible (god and religion are things i believe can be separated), and that i don't let them manipulate me. In reality, how dare anyone say that they know what's going to happen to your soul when your meat suit fails. In light of that, how dare anyone say that they speak for, or on behalf of god (such a big corruption on belief in god to manipulate others).
The other part offense is that they believe that they are morally and religiously superior to me. These people i don't tell to **** off directly and just let my tolerance and acceptance of others piss them off even more. I'm almost damn well convinced that most christians just hate jesus and his teachings through their actions, selfishness, and corruption.
In short, it's all so saddening, because one of the first things to go in religion is humanity because of intolerance. Not many realize that only humans care if you were a good christian, muslim, buddhist, etc., and that the higher powers that be doesn't.