Destruction means obliteration of the statehood of Bangladesh, in another word India will occupy Bangladesh. But you should dread such prospect because unintentionally you will open the Pandora's box of disintegration of India and emergence of Greater Bangladesh. Many times your hindutva gurus have warned that, once Muslim cross 30% thresh hold of total population in India, it will become a de-facto Islamic state where Hindus will be forced to live like a minority. Ask Subramanian Swami. India already home of 25 crore Muslims, add 17 crore from Bangladesh, 30 percent thresh-hold will achieve!
Moreover, absorbing Bangladesh will make the entire Eastern part of the country(West Bengal+ Bangladesh+ Assam) a Muslim majority area where Bengali Muslim will dominate numerically. Then Bengali Muslims from Bangladesh, West Bengal and Assam will start liberation war for secession from India and establishment of Greater Bangladesh. It will be a situation 100 times worse than Kashmir. Foreign hostile powers like China and Pakistan will overtly and covertly support such movement. Remember, capturing Bangladesh will eliminate the problem of Chicken neck for India and weaken Chinese advantageous position in Arunachal Pradesh and Doklam. So China will do everything so that India can not establish a farm grip over Seven sisters states. Supporting Greater Bangladesh movement will be very logical to achieve that cause.
These are the strategic calculations which prevented India from taking any action against Bangladesh in the past when hostile BNP was in power in Bangladesh and ULFA and other separatists took shelter in Bangladesh. There were serious border clash between BSF and BDR in those days. Many BSF soldiers were killed by BDR.
en.wikipedia.org
A news item from 2005.
2 BSF men killed in Saturday's clash with BDR, bodies handed over
Two Indian Border Security Force (BSF) personnel were among the dead in Saturday's skirmishes between the Bangladesh Rifles (BDR) and the BSF along the Akhaura border.
bdnews24.com
Despite all of those, Then Indian PM Atal Behari Bajpayee invited Khaleda Zia to India and discussed about ''co-operation'' !
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So, reality is very different from false bravado and suppa pawa bragging in PDF.