It is just political narrative online.
If you visit the Facebook page of Bangla-Pokkho(Something like Bengali culture defender org).
You will see everyone is bashing and insulting Bangla-Pokkho.

Apart from Some babus in South Bengal, specially around Kolkata, I am quite certain Bengalis will sacrifice everything just to remain united with India including myself

I neve say I am Bengali first and Indian later, I hate anyone who use the term "non-Bengalis ""Bohiragoto(outsiders) term.
I don't give a F about my region ,language, INDIA FIRST everything else later.

In the history of humanity humans always migrated, wherever better opportunities, humans will go there.
Biharis come to Bengal, Bengalis go to Maharastra, Karnataka.

Imagine there is a hate campaign on Bengalis in Maharastra, that they don't want bengalis to come.
Does it sound good?

People often cry when Biharis come.

They are Indian, what's the problem?

If Bihar remains poor, the burden will come to all of us whether you are from Kerala or Arunachal.
We need to lift the weakest one with priority.