This is just a small sample of the convention's rhetorical drift so far. The Democrats have decided George Bush is guilty of every charge imaginable until proven innocent, and they are not interested in considering any evidence to the contrary. Admittedly, that's the nature of conventions, which are essentially giant choirs hungry to be preached to. Nevertheless, what varies from convention to convention and party to party is the credibility of those assumptions, and here the Democrats come up wanting.
The Boston Democrats take it as a fact that George W. Bush deliberately divides people, and for bad reasons. Time and again, Clinton insisted that Republicans "need a divided America." Jimmy Carter accused Bush of lying, or of "manipulating the truth" about the war in order to "generate public panic." The analysis behind such convictions goes something like this: George W. Bush enjoyed an astronomically high approval rating after 9/11 and the war with Afghanistan. But for political motives no one can explain, he chose "to divide" Americans and risk that popularity by "lying" about a war we didn't need to fight.
None of this is supposed to make sense on a rational level. These are expressions of faith. And for the Democratic Party, a Republican is by definition "divisive" whenever he does things Democrats don't like. It's similar to the way Democrats bang their high chairs about "wedge issues" - which is to say, issues that work better for Republicans than Democrats.
Speaker after speaker insisted that President Bush was a dangerous unilateralist who broke the common bonds of the international community. Among the evidence cited by Bill Clinton was George Bush's refusal to participate in the International Criminal Court and the Kyoto treaty. Never mind that Clinton took pretty much the same position when he was president. Bush is a dangerous maverick! Similarly, speaker after speaker took John Kerry's word for it that he has the sort of charm necessary to persuade the "international community" to share the burden in Iraq and Afghanistan it now refuses.
In other words, as with Homer Simpson, the Democrats are in denial. Homer thinks that someone else needs to clean up the messes in our homes, that somehow it's unfair that we should do our own dirty work. The Democrats have convinced themselves that George Bush unfairly - "divisively" - interrupted the holiday from history that was the 1990s. This is all nonsense, of course. But that's beside the point.