after many incidents and involvement of police and army themselves (pakka kila massacre) altaf hussain ordered the community to protect themselves, and thus the order to sell tvs other household items to buy weapon licenses. the community started to defend itself, and it got little out of hand because when ever mohajirs were attacked it saw a more fitting reply, the others started taking their bodies to pathan KPK, punjab area etc to show how cruel MQM was, which in real was not MQM but mohajirs trying to defend their homes from drug lords, klashnikov culture afghanis who were armed with weapons like anti aircraft guns, rocket launchers, hand grenedes, all used in afghan wars, pathans or afghanis used to despise mohajirs and raped many mohajor women, killed mercilessly by butchering people up
when the news reached punjab, the army belonging from punjab landed in karachi, thus rangers were deployed and punjabis started calling mohajirs hindustanis, indian agents
the army started operation of 1992 on bogus claims like jinnahpur, torture cells, it justified the operation using the kind of propaganda which the two rival countries do, jinnahpur map was printed on the front page of jang news to show that mohajirs had become separatists and thehelp from indian RAW, torture cell stories were published to show that MQM was butchering punjabis which created hatred among punjabis and pathans up in the north completely ignorant what really was being served by their so called genetic and racially superior fellows as compared to weak hindustanis
and then haqiqi faction was made in 1993 to counter MQM, the notorious people who were hard core criminals which were kicked out by MQM because of their violence were given money and weapons to finish off the MQM( and that time MQM decided to shift its major leadership and brains abroad so that party remains intact people like haider rizvi, waseem akhter, faisal subswary, saleem shahzad, imran farooq, altaf hussain, ibad ul rehman, nadeem nusrat, mustafa azizabadi), these criminals recieved official support from ISI chiefs and nawaz shareef until musharraf deported ganja to jaddah
to say it was a reaction yes it was, but it wasn't on the scale which happened in east pakistan, the punjabis were not dragged no karachi streets, pathans were not killed because of their race and shot in front of the public like what mukti bahinis meted out with urdu speakers and pakistan force that time, it was just a fight between the army faction(haqiqi) and the MQM