Apostasy and heresy are very much part of Christianity and the penalty is death - usually by stoning. Most of these barbaric laws and penalties come from the Old Testament you know, the OT is part of Judaism, Christianity and Islam. I'm not sure exactly how many people the Inquisition burned for heresy and apostasy but it's substantial and of course the Reformation and Counter Reformation burned a fair few more here. If you're interested have a look at the history of the Cathars in France - Christianity in its full glory. Of course Christians tend to ignore the laws of the OT these days, there's no reason to believe Islam won;t do the same.