Its the Pak army (Rangers) who ve been killing muhajirs since early 90s in the name of clean up operations. They are the one who are behind land mafia, tanker mafia and turning a blind eye from corrupt feudal of PPP just to keep their stronghold of the economic nerve of the city (and country). Its the pak army who openly rigged elections to get PTI selected, its the same army who in past created MQM Haqiqi, PSP and forcefully stole the mandate of the Urdu speaking people.
Pak army to most part is a punjabi army, all police officers in karachi are either from punjab or interior sindh. Therefore Muhajirs are fed up from the Pak army and their dramay baziya.
Due to all these reasons, Muhajirs have valid reasons to be disappointed with the Pak army, which is just like an oppressing force for them.