Sigh Great. Its one of those guys. Stop trying to make him question himself.

"Look. It ensures peace because its part of a promise. Before the Districts would send Tributes to the Games as a sign to the Capitol that they wouldn't cause another devastating civil war like back in the Dark Days. Now, the Capitol brings in you guys from other places as their way of saying that as long as the Districts continue to behave like they should, the Tributes representing their Districts in the Hunger Games don't have to come from their...well. Their Districts."

Its an easy, nice justification. Isn't it?