Pakistan is a backwards theocracy, which created the Taliban and has been attempting to spread their awful model of governance ever since. I imagine they wish to set an example.
Pakistan created the Taliban out of political necessity, and the United States is to blame for it. When the USA and Russia fought a proxy war in Afghanistan, it left the country in tatters. Pakistan got millions of refugees (1/5 of the population of Afghanistan was living in Pakistan at one time). Think of how Americans start to hyperventilate even at the thought of accepting a few thousand refugees. Pakistan took in millions - and it had to stabilize Afghanistan to restore order and stop the flow. At that time, Pakistan supported the Taliban so that the mess that the United States and Russia made could be controlled. Blame the Cold War, not Pakistan.
It also has a different set of laws, added later, that is based on Sharia.
Did Pakistan have its blasphemy law in its current state since founding, or was it significantly broadened under Zia-ul-Haq?
I'm genuinely curious about this, because if it's a later addition, then wouldn't several decades of Pakistan's existence without laws as stringent as they are today indicate that the society can actually handle this being dialed down quite a bit just fine?
The hardliners' response to your last argument gets tied up in something like "the British took us away from true Sharia" or something along those lines. On talk shows you hear "This is a law from Quran and Sunnah, not a man-made law"