The purpose is to seal the border, whichever way you see it.
What is ruthless: People coming in from Afghanistan and killing tens of Pakistanis or people trying to cross border illegally and die in the processs.
By the way: Indians shouldn't be saying "we" when talking about US, UK, coalition.
Sealing that long border especially when people look so much alike is not possible. Equally importantly, we (India, US, UK ....) are quite interested in ensuring Pakistan achieves peace, law & order and social stability, since that is the only way to stop terrorism in the long run.
don't understand your parsing the 'we'...pls elaborate?