Quota IS RIGHT till all other parts of the country - no mater in what province, have similar education/ employment resources as Karachi.
Remember, Karachi is not property of anyone, neither are its resources. Every Pakistani has right to use them, but of course the ones who live here, are more blessed in that way, that they dont need to leave their home/family to get into those institutes because the institute (academic or professional, for education or employment) is already close to them.
those who make noise about quota, most of them are either biased, or have actually no knowledge about what conditions their other Pakistani brothers, live in. Go visit interior sindh, or baluchistan, or Punjab and go to our beloved NWFP, and you will say yes, we should have quota for those less-privileged ones, only if you want to be fair.
having said that, YES quota is NOT ALWAYS used fairly, and sometimes its misused, which needs to be pointed out, and treated on case-to-case basis.