It is the rejection of reality that Jesus rebukes as Satanic.
Much like Eckhart, the 20th century philosopher Simone Weil described the perfection of the spiritual life as the consent to be nothing - to recognize and accept the reality of the world, and to love it, “not wanting to tamper with it.”[1]
It is only when we trust grace completely, and there is no fear of judgement or condemnation that we can practice consent to reality without wanting to tamper with it by making it better, purer, holier, safer.
It is grace that allows us to see beauty in ugliness and God in all things and enables us to stop rejecting one thing over another.
It is grace that enables us to cease crying out, as Peter did when he rejected the idea of Christ crucified, “God forbid it, Lord! This must never happen to you!” (Matthew 16:22, NRSV).
It is this very impulse to reject and the lack of consent to reality that Jesus rebukes as Satanic in this story.
[1] Simone Weil, Intimations of Christianity Among the Ancient Greeks, (London: Taylor and Francis : London, 1987), 101.