I see his point. His vision was to create a game for the entire family, one that they could all enjoy, and that wouldn't be hard for new players to get into. Sure, it turned out differently, and he could be a bit more supportive, but in the end, the competitive smash scene kind of goes against what he believes in.
However, as he said, people are free to play Smash however they want, and that's the cool thing about the game, whether it be 1v1 no items omega or free for alls with all items on in palutena's temple.
It's all about what kind of player you are, and Sakurai himself is just a person, he wouldn't prohibit you from playing the game the way you like.
It just isn't his preferred playstyle, the guy's just being honest.
But if he didn't care, then there'd be no For Glory mode.