"On Thursday, we made some critical personnel decisions to secure financial flexibility for player moves now and in the future in order to give you the best product on the court."--Nets president Rod Thorn, e-mail to season ticket holders, June 28 (via NetsDaily)
I suspect Hemmerdinger meant that an arena in Brooklyn was a "good thing for the public," rather than a public good.
In other words, like national defense, or air, or (free) television.
Not an arena with a finite amount of tickets and a "product on the court."