I'm not sure what makes him different than any other sports radio caller. If anything, he sounds just as dumb as the people he's calling dumb.
The perfect analog for me here is Pop. They're so similar - only about a year and a half apart in age, they won a bunch of championships with different rosters over multiple decades, and when their star talent wanted leave, they opted to try to keep going for playoffs, which resulted in multiple years of middling success before sadly bottoming out.
You could sit there as a Spurs fan after last season and say "Oh, you morons want to get rid of this guy, he's a genius, he led us to all these titles, he's going to give us the best chance at winning in the future, you're all dumb for thinking he's past his prime, he's going to get Wemby and kick ass." Okay, yeah, we've had a lot of that in these threads recently. But do you think Spurs fans are feeling awesome about that now? Despite the amazing rookie with a 7% block rate, they're one of the league's worst defenses... their only good lineup is Wemby at Center and they never play Wemby at center... their young talent around him is stagnating... Do you think they'd rather the Spurs tried to find the next Mark Daignault or Will Hardy or someone of that ilk? I would if I were them.
Nothing gold can stay. It doesn't take away from their amazing runs to believe that someone hungrier with a different perspective and, yes, younger would lead to better opportunities for the franchise over the next 5-10 years. It's going to happen eventually, and probably sooner rather than later.