Of course what you're saying is true. However, you're dealing with people that believe a market economy is fundamentally unethical. They believe that benefits

Of course what you're saying is true. However, you're dealing with people that believe a market economy is fundamentally unethical. They believe that benefits such as housing should be assigned entirely according to the individual's need, not how much money they are willing or able to spend on it. And who better than them as the judge of neediness? So of course it makes sense that you have people protesting this development in the article, demanding that 100% of the units be "below market rate," despite the obvious economic unfeasibility of this. After all, profit taking or "rent seeking" is inherently unethical and exploitative. They may have prevented 75 units from getting built, but at least they stopped a developer exploiting people's need for housing for profit. And, as a bonus, they send a message to other developers that you defy them at your peril.