In a world without insecurity there'd be no schadenfreude, but hey, we're hardly in any danger of such a world emerging any time soon, so let's acknowledge that unjustifiable joy.
Avoiding the guilt of feeling happy about another's failures requires that other to be perceived as something of a pompous or arrogant jerk who is deserving of having his downfall be applauded. The easiest places for this is in competitive pursuits—namely sports and politics.
Given that many of us are not professional athletes we probably harbor some latent envy of how those guys were lauded back in high school. Combine that with the exorbitant salaries garnered by even minor players and the inflated egos of the more "colorful" players, coaches, and owners, and it gets easy to delight in their losses.
It's not good, but it's understandable, and relatively innocuous.
Just the other day I saw that the Cowboys had lost their second game, and felt a tiny cheer escape me. A couple weeks back I gave an excited air punch when I saw the highlights of a Yankee defeat (something of a rarity this season). Those games had no bearing on any team for which I may have been rooting; I was merely glad to see those teams go down.
Logically it makes little sense. It's not as though I think every player or coach or person associated with the "Bronx Bombers" or "America's Team" is some horrible scoundrel deserving of defeat. And the reality is that if any player who previously was on one of those teams got traded to a team I supported I'd root for his success with the same enthusiasm that in the past I'd devoted to his failure.
Politics is different, for the obvious reason that the failures of politicians often translates as detrimental to me, either as a citizen or as a taxpayer (or both)—and sometimes their ostensible victories are bad for me as well. One sort of has to root for politicians to achieve what for lack of a better term we'll call a victory, and hope that it's a win for the rest of us.
Well, roughly half of us.