We are studying this issue in my class this week and my instructor gave us a great example about the causes and impacts of religious harassment from India.
In India, religious differences are often the cause of violence between communities, as is in many places in the world. People tend to be really sensitive to religious comments in general because religion is one of the pieces that make up our identity and culture. So when someone is harassed on the basis of their religion, they feel that their whole being is under threat.
This becomes a bigger problem when leaders and authorities also choose sides and choose to ignore or even promote religious harassment. For example, in some local Indian governments, this is sometimes done to gather votes from Hindu, Muslim or Christian voters.
There are different types of harassment but religious harassment is one of the most dangerous because it can easily lead to violence and often goes both ways. My instructor said that religious riots in India are a great example of this.