How does religion accentuate differences and conflict in society?
It encourages judgmental behavior, socioeconomic segregation, and the objectification of women. Amongst the classes religion justifies hatred of the poor in the rich by claiming that they are stupid and lazy. In the poor it encourages hatred of the rich by calling them greedy and selfish. It encourages people to be wary of people of different ideology by inventing a paradise suited only for the select few who believe. Almost all religions have a belief that women are subordinate to men and are property that can be sold traded or inherited. People in high position in society and government use religion to rationalize their stance on secular issues and basically condemn those who oppose them. Religion calls together armies to war against each other, separates families from loved ones and spreads fear.
Overall I would say that Marx is spot on when he said that religion represses social change and is an opiate for the masses.