I think anyone with any common sense and decence can see why this comment was deeply offensive and wrongheaded. (See Sullivan and Tapped for examples, though. And see Brendan for why it's ironic to be linking Sullivan in this context.)
It was obviously Rove's intention to smear all liberals, and quite possibly all Democrats, with his phrasing (why else would he say: "No more needs to be said about the motives of liberals?">. But even in the few specifics he did mention, he lied. Ironically, the examples are what conservatives have been pouncing on to defend Karl. Redstate.org has a take along these lines that generated a link from Jonah Goldberg on The Corner.
RedState gives Rove more context than he got in many media reports by quoting him saying this:
MoveOn.Org, Michael Moore and Howard Dean may not have agreed with this, but the American people did. Conservatives saw what happened to us on 9/11 and said: we will defeat our enemies. Liberals saw what happened to us and said: we must understand our enemies.
Then RedState.org add this brilliant analysis:
Comment: here Karl Rove specifies whom he is talking about MoveOn.org, Michael "Fahrenheit 9/11" Moore, and Howard "Interesting Theory" Dean a/k/a the guest of honor in the presidential box at the 2004 Democrat National Convention and the current chair of the DNC.
Little problem here: Howard Dean didn't respond to 9/11 by saying we should understand our enemies. Remember that little war in Afghanistan that was actually about punishing the terrorists who attacked us and the nation who shielded them? The one that has largely been pushed aside to pay attention to the invasion of the country that never attacked us? Howard Dean supported it. As this website with profiles for the 2004 presidential candidates quotes Dean:
"Our military has done an absolutely terrific job in Afghanistan, which is a war I supported" and "I supported the war in Afghanistan; 3,000 of our people were murdered. I thought we had a right to defend the US."
In other words, Howard Dean had the same reaction to 9/11 as "conservatives" in Karl Rove's calculation. He is right that dumbass Michael Moore opposed the war. And current MoveOn.org leader Eli Pariser was circulating a petition asking for restraint, though the actual organization wasn't behind it, I believe.
If you want to smear liberals, it's not like it's hard to find 3 hard core lefties who did oppose the war. Rove is counting on the fact that most people just associate Dean with the hard left due to his strident -- but prescient and accurate -- opposition to the Iraq war. What a truly vile human being he is.
But he's possibly smart, if he had this all planned out, since the debate has now become whether this is as bad as what Dick Durbin said, rather than the merits of Rove's assertion. I think the two are clearly not comparable, since Rove smeared all liberals using lies, whereas Durbin made inflammatory comparisons in the context of a very fair and factually supported critique of our treatment of Guantanomo detainees (Brendan has a good analysis of what Durbin said that I agree with 100%).
NY Gov. George Pataki's response shows exactly how the right is going to respond thanks to the mostly bullshit Durbin controversy: "I think it's a little hypocritical for Senator Clinton to call on me to repudiate a political figure's comments when she never asked Senator Durbin to repudiate his comments." Of course most people paying only casual attention to politics will probably think both sides said something offensive and dismiss this all as more political bullshit.