Reality was opposite what people thought. People in West Pakistan were kept in dark for so long- they were just denying without realizining ground facts. Bangladesh was already carved out in reality at that time. Not accepting was not an option to any one. It was just like a 'pegeon closing eyes in front of cat'.
You are saying Pakistan would not have established diplomatic relations with Bangladesh, one of the biggest Muslim country? What a silly idea.
Bangalis are just like our Muslim brothers who suffered for long time in the hands of West Pakistanis, same as Blochis suffering now. If majority of people living in Blochistan want to live independently then their wishes should be respected. This is called democracy. Refrandom in Scotland will go ahead next year asking people whether they want to stay with United Kingdom or not. This can only happen in civilized world.