Incidents related to that have to do with religious extremists persecuting Shia's, but that is mostly confined to the Tribal areas and some parts of KPK province due to lack of education and exploiting on part of the extremist mullahs. You won't find such things taking place in Progressive regions of Pakistan.
Before the 1980's Soviet occupation of Afghanistan, attacks on Shia's and similar incidents were mostly unheard of in Pakistan. Most, if not all, Pakistanis followed a Sufi influenced Sunni Islam and no one even knew who was Shia or Sunni, everyone prayed in the same Mosques, celebrated the same holidays, intermarried and coexisted peacefully. This was mostly due to the fact that when hindus were slaughtering Muslims in 1947, and train loads of dead Muslim bodies were coming to Pakistan, they didn't ask those people which Sect they belonged to before butchering, raping, kidnapping and looting them, they slaughtered them because they were Muslims, and it was this tragedy that left its mark in the minds of the old generation that they (our enemy) committed those atrocious crimes against us because of our common faith and our desire to have our own Nation where we could go to the Mosques without having to worry about someone tossing pig heads into the mosque or some safron gangs bullying our people and preventing us from worshiping our Lord, a Nation where we could preserve our ideals and our distinct identity, and SubhanAllah we got that homeland in the form of Pakistan, achieved after so much sacrifices.