I don't think so. Sure, many observers have noted that Nets fans are not as passionate as Knicks fans, or other teams with more established fan bases. But the Nets filled 94.9% of their arena, while the Knicks sold 96.3%. And the Nets, of course, sold a lot of gear, fourth in the NBA.
The authors of the study, at Emory University, finally put up some backing data (at my and others' request):
I don't think that helps much. The Knicks' attendance edge is magnified by an arena with greater capacity, and the willingness of Knicks fans to pay more has less to do with passion than a longstanding monopoly position in a large market.