Pakistan People's Party (PPP) Chairman Bilawal Bhutto Zardari has said that the "Sharif-Modi friendship" was causing irreparable damage to the Kashmir cause.Bhutto on Sunday condemned the killing by security forces of civilian demonstrators who took to the streets in thousands after the death of a top Hizbul Mujahideen leader, Burhan Wani, Dawn online reported."Such aggression by Indian authorities has exposed the sham democracy prevailing in India," he said.Bhutto accused Nawaz Sharif of damaging Pakistan's foreign policy by giving his Indian counterpart Narendra Modi a "certificate of friendship".Bhutto, who returns from London this week, is to address rallies in Pakistani Kashmir, an aide said.