The conflict perspective is one of the three main perspectives in sociology. In this perspective, all aspects of society come about because of conflict between the dominant classes of society and those that they have subordinated. In this perspective, religion is simply another way for those who have power to keep that power and to maintain their dominance over other groups.
There are at least two ways in which a conflict theorist would say this is true. First, it can be true on the basis of class. Marx is famous for having called religion the “opiate of the masses.” What he meant is that the upper classes use religion to persuade the lower classes to be content. Christianity, for example, tells us not to worry about our status on this earth because it is our eternal life that is more important. This might encourage us to accept a subordinate status in this life.
A second way in which this is true is on the lines of gender. Many Christian sects teach that women should in some ways be subordinate to men. This (one can argue) is an example of men (who are dominant) using religion to maintain their dominance. They get women to believe that their lesser role in society is the will of God, not the product of oppressive action by men.
In these ways, the conflict perspective sees religion as a way of allowing dominant groups to maintain their position in society.