Politics of MQM has from day 1 been based on ethnic hatred, lies and playing the victim card. I will write about some of the myths created by MQM and spread hatred against other groups of Pakistan. In doing so they have created various lies. One is that punjabis stopped migrants at time of partition from settling in Punjab and they were forced to settle in Karachi. And one thing that you will always hear from them is that at time of partition, Lahoris lined the Lahore railway station with sticks and prevented people from deboarding, telling them, "*Pakistan aggey hai"*
"Pakistan aagay hay" is not a myth, but never heard "Lahoris lined up with sticks. This term "Pakistan aagay hay" was told by grand-parents who actually migrated after Pakistan's creation.... not a 'heresay'.
Also notewrothy is that lot of those people that settled in Karachi did not come through punjab but entered Pakistan through KHokhrapar border, which is in Sindh and was closed after 1971 and recently was re-opened.
My family entered Pakistan through Lahore side and continued to move southwards (reason above).
The other myth is that of deprivation of urdu speaking community at expanse of others. And major reason for cited for it is the qouta system. The qouta system was rigorously enforced by Liaqat Ali Khan and at one time 60% of jobs were reserved for migrants (A copy of this notification was presented in MQM vs Gov of Pakistan petition 1994). Hence the migration and settlement into Karachi (which also was capital then) continued well into 50s.
I don't know what the job situation was back then as my family was from farming side and no one was 'educated' (hence not eligible) for 'sarkari-jobs' but we did hear about army asking about "where are your parents from? Pakistan? what about your grand parents?"
As burqaposhx mentioned, these myths were not created by MQM, rather used for political mileage.