It’s a superiority complex that the Bengalis of Calcutta have. They look down upon anything not related to them.
Most of the Bengalis of Calcutta have two different origin. The Bengalis who resided in the city for more than 150–180 years, the others are Bangladeshi immigrants. The second are the dominant.
They have a tendency of dominating everything and when they do not win they use tactics to demoralize the opponents.
Like, they mock the Bengalis of Midnapore and Bankura district for their strange accent, not realizing their own accent is extremely hilarious.
They have a superiority complex over the Bihari and UPites as these people mostly come to Calcutta to do menial jobs and these Bhodrolok babus of Calcutta gets a reason to mock not realizing that not any job is small.
These things are mostly cultural. I am a resident of West Midnapore district and I have faced these problems from the residents of Calcutta!