Who Should We Root For?

In an earlier post, I mentioned Ayn Rand's open letter to Boris Spassky, and one part of the letter really grabbed my attention. After writing that she and all her friends are rooting for Fischer as protest against the Soviet regime, she lists in the very next paragraph a series of Fischer's bad behaviors: "He throws tantrums like a child, breaks agreements, makes arbitrary demands, and indulges in the kind of whim worship one touch of which in the playing of chess would disqualify him for a high-school tournament."

But between Fischer's misbehavior and Spassky's supererogatory behavior during the match, I found her decision to root for Fischer puzzling. (Not necessarily mistaken, just puzzling.) Of course, there were mitigating circumstances in the case of Rand and the Fischer-Spassky match, but I'm interested in the general question: should one root for the worse sportsman (no pun intended!), just because he or she is one of "ours"? That is, are Americans justified in rooting for an American just because he's American, or men for a man just because he's a man, etc., even though they know that the opponent is otherwise more admirable. All things being equal, it's unproblematic, but if things aren't equal, then what?

Discuss.