Your assessment is full of bs.
Karachi was Hindu majority before partition.
SINDHI REFLECTIONS
June 1947: The British announce the Partition. The first wave of migration from Sindh.
August 14-15, 1947: Withdrawal of the British, the birth of independent India and Pakistan, with Sindh in Pakistan.
August 19, 1947: Riots in Quetta, many Hindus killed (see Lila Kripalanis account.)
August 20, 1947: Second wave of migration (see Dr. Ram Buxanis account.)
August 27, 1947:
Riots in Nawabshah organised by Mr. Masood, the Muslim collector of Nawabshah( see Gul & Pahilraj Ramchandanis account.)
September 1947:
Curfew in Hyderabad Sind. All Hindu families were informed that the refugees were out of control and that all Hindus were at risk( see A. Daswanis and Javhar Advanis accounts.)
November 22, 1947:
Riots in Hyderabad Sindh( see Chandru Gurbaxanis account.)
December 1947:
Hindu houses and businesses were marked overnight. The very next day Muslim mobs began open looting and occupation with the full connivance of the authorities (see Dr. Niranjan Dudanis account and also Shewak Nandwanis.)
Jan 6, 1948
Riots in Karachi and Hyderabad. The third and the largest wave of migration after these riots.( see Mangharam Sipahimalanis account as well as Meena Rupchandanis and Dr. Motilal Jotwanis accounts among several others.)
Jan-Mar, 1948: The highest numbers of Hindus migrated from Sindh to divided India. Most settled in the outskirts of Mumbai. The population of Sindhi Hindus before the Partition in Sindh was 14, 00, 000.
By 1950, 12, 25, 000 had left Sindh for India and other parts of the world.