Its a shame for me as a bengali that you have been to calcutta and you have faced problems. As a bengali I apologize for that.
However the population of Kolkata is pluralistic and not all residents in Kolkata are bengalis..
In India, if you go through news, people are not allowing people from others regions to stay in their state.But Bengal welcomes everyone irrespectyive of region/religion. Some one have said correctly that if you are doing right then get prepared to be in the receiving end.
Before anything let me clarify one point to you with regards to nepalese and people of Darjeeling.
Nepal is a soverign country and so is India.
But then you must question why people are against the bengalis? Its that the govt in West Bengal is led byt the communists and their stand in various issues like India US nuclear deal, etc is not taken down well by all. And they feel that by electing the communists for 31 years at a stretch Bengalis are doing harm to the country.
There is another point also. There is a huge influx of Bangadeshi Muslims in this state as this state has common borders with Bangladesh.
However Your comments of apologizing to India for some wrong doing from the part of bengalese is I would feel due lack of knowledge and based on some comments by others. If you want to read about bengalese you canm search for the bengali freedom fighters in idia, etc now a days you can have huge information from internet..