Juan: Unlike the ancient Olympic games on which they are based, the modern Olympics include professional as well as amateur athletes.
Conclusion (hence)
The presence of professional athletes violates the spirit of fairness essential to the games.
Intermediate Conclusion
It is unlikely that amateurs will ever offer a serious challenge to professionals in Olympic events where they compete against each other.
Evidence (since)
Amateurs rarely have the financial or material resources available to professionals.
The ancient Olympics did not include professional athletes.
Goal
We don't really need to worry about Michiko's response. We just need a way to accept that amateurs rarely have the resources that professionals have, but argue that amateurs might still offer a serious challenge to professionals and thus it's still a fair competition.
Or we can argue that even though the amateurs won't offer a serious challenge to professionals competing in the same event, the presence of professionals doesn't violate the spirit of fairness.