I am writing about this.
I think what people are actually blaming ZAB for is his failure to *prevent* takfir from being codified in law at one specific time period in the 1970s.
As to how fair that assessment is: it requires a longer & brutally honest discussion https://twitter.com/HashUrTag/status/1246829934347198465

I am very suspicious of Jiyala arguments to the effect that "What could Bhutto do?" etc.
There was *much* that he could have done. Whether liberals with a pretense to non-violence would stand by that is another question

But the Takfiri supporters of the 2nd amendment are correct in pointing out that what they support is a process & discourse (& series of violent episodes) that began well before the 1970s.