I think it shows an ugly side of human nature that people would take more pleasure in the downfall of another than they would take pleasure in the achievement of their own team. As a born-and-bred New Englander and longstanding member of Red Sox Nation, I hate the Yankees as much as the next guy. But when the Sox beat the Yanks, I'm happy that the Sox beat the Yanks. I'm happy for the Sox. I'm not as concerned that the guy wearing pinstripes feels personal shame and humiliation.
So, I'm not really into the chants of "Yankees suck". Partly because it's so patently untrue that the whole enterprise smacks of wishful thinking and is therefore more than a little bit pathetic. The Yankees are, historically and currently, the least sucky team in the history of professional sports. Why else would we bother hating them? And "Jeter swallows" is downright offensive. I will say no more on it, lest it be dignified. (As if such a thing is possible.) I'd rather cheer my team on than attempt to degrade another, no matter how much I don't care for them.
Which brings me to today's real point of contention, chanting "o-ver-rat-ed" at a team that is being vanquished by another, presumably underrated, team. This is taunting, of course. But, even more than chanting "[the other team] sucks", it paints the chanter as a bit ignorant and as someone who is actually dissing his/her own team.
Listen. If the other team is overrated, that means that they're not really as good as the conventional wisdom holds. Which means that when you're chanting that the other team is overrated, you're really demeaning your own team. "Hey, those guys really aren't all that good!" So, now you're crowing that your team just survived a squeaker with a team that isn't very good? What does that say about your guys?
Wouldn't it be more uplifting to say, "You guys are a very talented assemblage of physical prowess and game management. And the team for whom we cheer has defeated you, making them even more awesome and reflecting their glory on us who wear the same colors as we cheer!"
I reckon that doesn't make much of a chant.