This is quite different from the Christian doctrine of Atonement.
It was the spirit of co-operation which Islam engendered among wild and unruly Arabs, that enabled them to put aside their tribal feuds, to unite and conquer more than half the known world in the first century of the Hijri era (= the 7th century of the Christian era). It was the lack of that spirit in the next two centuries that dismembered the Muslim Empire.
I say "the Islam of our ancestors", because the Islam of some of our contemporaries, called Muhammadanism, is not quite the same.
Read Prof. Gregory's Discovery or the Spirit and Service of Science.
"Sufis" are those Muslims who claim with Mowlana Rumi
ماز قرآن مغزرابرد اشتيم * استخوان پيش سگان انادا ختيم
"We have taken the marrow out of the Qur'an and thrown the bones to dogs," meaning by "dogs" those who quarrel over words (متكلمين) of the sacred texts.