That guy is a moron. The government can literally amend the law and the municipal code to eliminate collective bargaining and striking rights, create a Police Personnel Code based on ranks and other criteria, and any court would held that constitutional because they are law enforcement personnel.

That said, the City requiring residency to its employees, including police, is in my opinion legal negativism that should be declared unconstitutional because it takes into consideration other criteria different from merit and qualifications of the job.

To be clear, an applicant literally need to be already be a resident of the city prior to applying just to qualify for an interview, so this is not about someone interviewing and vouching to live in the city after being hired. That's nativism and a gross violation of merit principles, because Chicago needs to settle with their natives at the moment of interviewing, instead for interviewing and hiring the most qualified prospective applicants. Also, most law enforcement officers elsewhere are not forced to live in the towns they serve for security reasons because they might be targeted by local gangs, so it's actually reasonable to allow them to live outside the city.