Occasionally I encounter Christians who insist that their religion is morally and ethically superior to other religions, particularly Islam. Although I will readily agree that Western societies are on balance better places to live than Islamic societies, I do not concede that this is owed to the influences of Christianity.
Murdering heretics is profoundly uncommon among modern Western Christians. However that is not because Christian doctrine doesn't allow it. It is owed to the secularization of those Western societies. A process of moral progress that has been (and still is) hard fought by Christian leaders at each step. Yet it has happened, dragging Christianity kicking and screaming out of the Dark Ages and eventually into the 21st Century, while denying religions much political power.
Islam is a different case. Yes, we can find secular Muslims, but overwhelmingly Islam is intermingled at every level of those societies that are predominately Muslim. This lack of secular influences on politics and social expectations is preventing the advancement of most Muslim societies, leaving them mired in obsolete ethical systems, very much like Christian societies of medieval Europe. Pretending otherwise is drawing a poor distinction between religions that if taken to their fundamentalist extremes uncorrupted by secularism are little different from one another. Which is a danger of religion in my view. Even in moderate forms, its literalist and unethical roots lurk within the theology ready to be embraced by fundamentalists.
The process of secularizing Western societies is only a few hundred years old, starting slowly in the Renaissance and picking up steam in the Enlightenment. With a few noteworthy but brief confluences of time and place, the various ages of civilization before the Renaissance are largely indistinguishable from one another in a moral sense. Local or religious flavors of the same barbarity, cruelty, and tyranny that almost universally defined the wielding of power. Power that was so intertwined with religion that it is hard to separate where the church ended and the state began.
Or to put it another way, religions as we recognize them today, have had at least 3000 years in which to progress ethics to the betterment of humanity. Which they all failed to do, despite possessing enormous resources and influence. It wasn't until religion began to be intellectually and politically marginalized that the process of developing humane societies began to see any real progress. Which is not to say that social progress is anywhere near completion or that there have been no setbacks. But on balance, Western civilization has come further in the last 200 years than in the previous 3000.