There's no excuse for this obviously.
But if you're trying to make this a Muslim apologetic by saying 'Christians do it too', it's kind of weak. The problem is death for apostasy is prescribed in Islam and not Christianity. When people are stoned for apostasy in places where strict sharia is enforced, groups of Muslims will stone an individual to death. If you ever have a chance to watch a clip of a stoning do yourself a favor and pass on it. It's disturbing.
Also, you can't tell from the account whether the man happens to be Christian or whether he [thought?] he was acting on Christian principles.
Jesus did away with stoning in the Gospels. John, I think.