Bangladesh was not nearly as linguistically or culturally different from Pakistan as Kosovo from Serbia or South Sudan from (north) Sudan. Bangladesh is culturally (Sunni Muslim) more culturally similar to Pakistan (also Sunni Muslim) than East Timor (Christian) is to Indonesia (Muslim). Both Bangladesh/Pakistan and East Timor/Indonesia speak very related languages, so this isn't a difference between them. Overall, this is a very incorrect statement from you. And in all four of these examples the dominant country treated the breakoff country more or less the same.