MQM had the largest role to play. MQM's politics, headed by Altaf Hussain is based entirely on an ethnic agenda. .
Ok we agree MQM and Altaf Hussain are bad/terrorists etc etc... Many muhajirs/Karachi'ites say that too. But the problem is, we who are born and have lived all our lives in Karachi have seen the PPP and ANP(who have a handsome presence in Karachi dating back to late 70's and Karachi was infact once even called the largest Pakhtun city in the world) have seen these people firing, killing , stoning each other. Our cars, school buses were attacked on day to day basis. Sohrab Goth, Sabzi Mandi, Federal B Area, Gulshan, Nazimabad all areas were like war zones. It's not like MQM was just killing randomly , it was almost a civil war kind of a situation where all these parties(PPP/ANP/MQM) were fighting on ethnic lines and killing each other party's members and innocnet people caught in between. And then came the operation 1992, although it was mostly directed against the MQM, but many in Karachi/Hyderabad took a sigh of relief as atleast there was some normalcy in their lives. But again the problem lies where one has to accept the atrocities committed by each party that was involved.