Thank you for the opportunity to help you with your question!
It is true that postmodernist and social constructionists values clash/mesh with Christians. The main way in which this happens is that both of these group do not fully accept transcendence. All Christians hold a believe in the existence of transcendence especially in consciousness, something which constructionists highly disregard. Generally, postmodernists seek to question or even reject the intrinsic notion held so dear by Christians. In this case, they do not accept the idea of a reality which is see to be dominant but would always believe that there is another for of truth. Thus, postmodernists do reject the idea that there is totality of all different ways.
Please let me know if you need any clarification. I'm always happy to answer your questions.