Eh, while I agree both the Celtics and Yankees have too many numbers retired, that author didn't really give any good reasons on why they're setting the bar low.
When he was talking about the Yankees, he wrote :
Here’s the debate. For a team with the championship pedigree of the New York Yankees, shouldn’t a berth in Cooperstown be the minimum required for a retired number?
Yet when he gets to the C's, he says:
Yet there are also good but not great players such as Jo Jo White and Cedric Maxwell, plus role players Don Nelson, K.C. Jones, Satch Sanders and Frank Ramsey. Should their numbers hang from the rafters at The Garden?
Five of those six guys are in the Hall of Fame. So it should be a prerequisite in baseball but not basketball? Should jersey retirements have a more stringent selection process than the Hall of Fame?
He also talks about the number of championships and retired numbers for other franchises to demonstrate how out of whack the C's and Yanks are, but if anything I think he kind of disproved his own point once he brought championships into the mix. If you do the math, the Yankees only have 0.81 numbers retired per championship, that's less than every other baseball team he listed (Cardinals 1.00, Giants 1.13, Dodgers 1.67, and Red Sox 0.88). And while the C's have a higher retired number-to-championship ratio at 1.24 than the Lakers (0.88) or Bulls (0.67), they're still much lower than teams like the Cavs or Kings with incalculable ratios due to no championships but 9 and 10 numbers retired. If anything, it's the Cavs and Kings who are setting the bar so low.
Ring of Honor like Dallas has is definitely the way to go though, or a Monument Park like the Yankees have (which has plaques, retired numbers, and actual monuments).