As to why tanking is bad, you can't have ten teams trying to win, ten teams trying to lose, and ten in the middle. That makes for a horrible league. It hurts the game, it hurts the league, it hurts the fans. Maybe six years down the road the 76ers compete for a title, but more likely they don't and they have alienated a large part of that regions NBA fan base. You don't just get that back because now you finally drafted a superstar.
Eventually, if it keeps up, it is going to become a Washington Senators/Harlem Globetrotters kind of deal.