Stoning is a punishment for blasphemy in the Bible. People who believe in the Bible as the word of God are pretty mainstream, so stoning to death as a punishment for non belief is not ‘extreme’, but mainstream.
Before we accuse the Taliban of being mediaeval, perhaps mainstream Christianity should be brought into the modern world
As Steve has already pointed out above, stoning and other archaic practises are not only no longer insisted upon by the vast majority of Christians world wide, they are also effectively prevented by the secular legal system, since most nominally 'Christian' countries place secular law above ALL religious law...especially in relation to barbaric punishments. That is precisely the problem with the current crop of extremists in Islamic countries. They insist that their own strict interpretation the texts is the only valid one, and further seem to wish to apply it to whole populations, whose own views may be rather more enlightened.
And in some other countries, such as Pakistan and India..and no doubt others.. there is constant tension between the actual laws of the country..and the way in which some sections of the population choose to treat each other, with, for example, 'blasphemy' being 'weaponised' by some against others. And of course 'adultery' in such contexts seem to be always the fault of the woman.. never the man. Even rape frequently attracts condemnation/isolation of the victim, whilst the perpetrator walks free.
I worked for a while alongside a Muslim woman of Bangladeshi extraction. She was lovely. Witty, attractive and generally good fun..and with a wicked sense of humour. She wore a fairly cursory headscarf.. and always either trousers or a long dress, but she didn't hide her face or her figure. She was married, with a couple of young kids. One day I was muttering about reported stonings in Afghanistan or somewhere. Her initial reaction was to laugh.. because she thought I was joking. In her own experience and frame of reference, stoning was unheard of. She insisted that stoning was not a punishment which she had ever heard of, much less would condone.
Of course I'm not suggesting for a moment that all Muslims think like the Taliban, or ISIS, which is why I suggested that the Afghan situation reflects a 'sectarian' conflict within the Islamic world. There is no valid comparison to be made with mainstream modern Christianity, or in fact any other major World religion.