Because christianity's reform came from within the cultures that housed it, it was not imposed from outside. Muslims in the west are more "peaceful"? Really, that's what you're going with? Muslims in the west aren't becoming increasingly radicalized as their proportion of the population grows? Did you miss the past decade of history? Even if that was true (it isn't), if you hadn't noticed the vast majority of the muslim population in the world is not in the west. Muslims living here becoming slightly more accepting of western mores will not do shit to reform islam. The rest of the muslim world is in a vastly different course, and it is dragging the muslims of the west with it.
And the reform of christianity was not a peaceful, gradual process, it was triggered by massive suffering and civil wars. You may think it's selfish, but I have no idea why the west is somehow responsable for Islam's reform. Their religion has absolutely nothing to do with our cultures, in fact throughout history has ALWAYS been antagonistic to it.
And of course you agree with some of the points there Butan, it is literally the exact same rhetoric but applied to targets you find acceptable. All of a sudden it makes sense, no need for a thousand excuses or external factors to explain it. I don't blame the buffet cherry-pickers, I don't expect any religious people to be rational about an irrational belief. The problem is bundle of stickss like YOU, ready to accept any facile, bullshit excuse "explanation" as long as it saves you the trouble of appearing "racist", i.e applying the same standards to other cultures that you apply to your own.