There isn't anything wrong with urban gardening itself. The problem comes when anti-development groups impose policies to prevent any building from casting a shadow on anything. Greenery and open space are both good and important, and gardening is a fine hobby. But urban gardens don't feed anyone and if there is a choice between housing people in an existing city, or protecting an existing garden from shadows, we should choose the housing every time.

Same thing goes for rooftop solar power: it's fine, but protecting it is not important.