Cultural differences play a relatively unimportant role in interpersonal communication.

This is an incorrect statement. Because ones culture plays such an important role in how we communicate to begin with, to suggest that it has an unimportant role in our interpersonal communication is not factual. We need to have knowledge of each other in order to effectuate proper communication, which cannot be achieved without a basic understanding of each other's culture.

Disagree some people are atheists and some grow up in a religion but atheists is a group of people with certain beliefs just like religions