Chicago, Illinois, is a city with a deep division over public art. A case in point: The city’s controversial “Graffiti Blasters”  abatement program, which for the past 21 years has criminalized street artists and muralists, by linking aerosol expression of any kind with gang violence. Introduced in 1993, the same year as the classic hip-hop albums “Midnight Marauders” and “93 Til Infinity,” Graffiti Blasters – the name sounds like a lightweight racist take on the term “ghetto blaster” – became…