If I had son he’d be way too young for the Olympics. ;-D
If I was an Olympian and asked such a question I’d be flattered that someone thought I could compete in a different sport.
I think most non-Americans would have thought it bizarre if an American reporter asked them if they were intending to join an American sport when they were finished their Olympic career.
I don’t think Usain was necessarily being disrespectful, as much as he was simply taken back by (in his POV) a bizarre question.
I’d have to see the video tape to be sure on that point, but that is my suspicion, because I would probably have the same reaction in that situation.