I am aware of that. I am also aware of the Nellie massacre. I am not sure how far you read Assam's history. The dis-trust of Bengali language imposition originated during the British era who brought many Bengali babus from Bengal for administrative jobs to their newly acquired Assam(most of the current's NE states). The result was, from 1836 to 1873, Bengali became the official state language in Assam. and for a community whose identity is primarily based in the Assamese language, it was a big blow. Even in present time, in Barak valley of Assam, Assamese is not recognized as a state language. Some politically motivated leaders still keep talking about throwing out the Assamese language from the entire state. Only between 1991 and 2011, the share of Assamese speakers in the state fell from 58% to 48%. This is matched by a quick rise in the share of Bengali speakers from 22% to 29% during the same period. Let's be clear, Bengali is the fourth largest speaking language in the world. All the immigrants from Bangladesh are speakers of Bangla. The suspicions of Bangla as an imposing threat to Assamese identity will remain.