Hummm,I think your understanding the ethnicity matter about BD is somewhat cloudy to say the least.The reason for independent nation was not based on religion, culture or bangali ethnicity. It was based on mistreatment, dominant attitude, poor management, racial discrimination based on color,language etc.
We are Bangladeshi first.there are bangali,chakma,arakan,mog ,kooki,shaowtal to name a few ethnic groups in BD.
And the people you are referring are very few in groups, who wants to glorify the bangali chetona.which is a relatively new trend in BD.