Postmodernism and Christinaty

I searched many books about Postmodernism and Christianty.
Many Chistians think postmodernism and Christinaty does not belong together.
Evangelism is to persuade people to become Christians by saying the Jesus Christ is the God.
Christians believe this is the only truth. However, postmodernists rejects of the dogma, principles, or practices of established modernism. They believe there is more than one truth.
Then, why some Christians think postmodernism threaten the Christianity?
I think this is from the modern view. Many people only think about the opposite side. (bipoalr oppositions)
Good and evil. Life and death.
Truth and death of the truth.

Here is some comment from the book Belief in Media.

"The dominant framework for thinking about culture at the time was Richard Niebuhr’s formative work, Christ and Culture (Neibuhr, 1951). Aspects of Neibuhr’s five models of rapprochement between Christianity and secular culture were frequently questioned and debated. What was neither questioned nor debated was Neibuhr’s modernist assumption that it was possible to see religion and culture as two separate entities. There was little debate also on whether one could talk about ‘Christ’ without at the same time talking about culture. It was still possible with integrity to think of a single entity called Christianity or ‘The Church’ which was separate from the culture and what was needed to protect it from cultural contamination."