London set to elect first ever Mayor of Pakistani descent

While this killing was certainly a result of religious extremism, Karachi is more than just a battleground based on religious intolerance. It's a sectarian nightmare with communities engaging in massive turf wars for votes, money and power. You have Pashtuns, the remnants of the Sindhi community, the Mohajir community (refugees from India and their descendants), and people aligned with the PPP. Note that both the PPP and the MQM (the Mohajir party) are strongly secular parties and both are equally involved in the endless violence in Karachi.

One of Jinnah's biggest mistakes was making Urdu the official language of Pakistan (which only Muslim migrants from India could speak so they basically inherited all of the original civil service jobs). That bred tons of resentment and anger towards the Muslims from India and those refugees who gained wealth and power have fought violently to hold onto their power and wealth. In addition, the government screwed up by allowing other provinces to funnel all of the refugees to Karachi. Couple that with refugees from Afghanistan and the Tribal areas also coming to Pakistan and you have a full on disaster that to this day continues.

Also the violence between the parties means that media routinely get killed in retaliation for speaking out against a particular party or its ideology. Even the MQM who are by far the most secular party (to the point where their leader openly says that Pakistan should have never been created) will routinely assassinate members of the media and political opponents.