I believe Bengali speakers of Bangladesh are Bangladeshi,chakmas are Bangladeshi, even biharis who accepted Bangladesh as country are also Bangladeshi. Still some people always focus on Bangali identity for some reason.
Either they can't move from 1952 in Pakistan time, or they are simply just want to be a part of anarchy. I think he ( whom you quoted) exactly mean so.
In this present time there is no option to divide our nation, that's why identity Bangladeshi is correct, and harping about Bengali is unnecessary, because we already ( 98% or more) speak in Bangla. It's not 1952 but it's 2019 and Bangladesh is independent nation now.
So there is no way to divide nation with Bengali stuffs.