I would suggest a petition, with locals promising never to shop at the store if the land is stolen from this artist. To my mind, the most significant part of the Kelo decision aftermath was that they never built the shopping mall on the stolen land because it had become too controversial. If he can show the same antipathy, with a significant fraction of potential shoppers alienated, that may remove the market incentive for stealing his land in the first place. Granted, the consequence may come too late, but then at least there will be another example the next time that corrupt crony capitalists consider stealing private property for personal gain.
The City would be better off to raze a different, derelict block for a store. It should be preferable to relocate a handful of low-income families dotted amongst the boarded-up row homes than to finance any remotely comparable equal compensation for destroying an entire art studio installation covering half a city block. You get the feeling there is just stubborn vengeance at play here now. And it would very much surprise me if the principals in the PHA were white, since most of the City administration is minorities.