Secularism is very essential for the smooth functioning of a democratic country. In today’s world people go to other countries to work or do business. So you will find that people of different religions live in the same locality.
In the event of people of different religions living together in the same locality there is a possibility that people belonging to one particular religion being in the majority. If this majority has access to State power, there is likelihood that it will use it to discriminate and dominate the minority group which practices another religion.
In a secular democratic country any form of domination or tyranny, based on religion is in violation of the rights that a democratic society guarantees to each and every citizen irrespective of their religion.
Therefore it is important not to allow any one religion, even though it may be the majority, to violate the fundamental rights of all citizens. If this right has to be maintained it is vital to separate the power of the state from religious practices.