Why does Islam attack the foundations of Christianity

The fundamental beliefs in Christianity is that Jesus Christ shed his perfect blood on the cross so that his blood could atone for our sins and that the holy spirit could then come and guide us to a life free of sin if we just believe in Jesus Christ as the son of God and repent from our sins.

Islam claims that 700 years after Jesus lived they knew more about him than the Apostles and the eyewitnesses who lived with Jesus. Islam says that Jesus (who they call Isa) was not the son of God and did not even die on the cross which completely destroys the gospels and purpose of Jesus shedding his blood. This is an assault on Christianity.





Question: How does Islam claim they want to "coexist" when their quran actually attacks the foundation of Christianity and goes so far as to call Jesus a liar who fooled all his folowers and sent another to die in his place.