By stating that the US will not set any timetable for leaving Iraq, so as to not give aid and comfort to the terrorists. Rumsfeld is tacitly admitting that the issue is not a matter of dialog on an occupation timetable between the US and the Iraqi people, it is a pitched battle between the US and all of the various warring factions who are fighting to try to force the US to leave. Further, it is a battle the US assumes it would lose if it left any time soon.
Why does the distinction matter?
Why such a distinction matters is that the US is prevented from giving Iraqi citizens any clear date for US departure, a goal that would help the Iraqis see a clear rationale for supporting their political process. Instead, the country is left in the grip of those seeking to prove their mettle by attacking the US, thus cloaking their personal agendas with the mantle of patriotism.
If we went into Iraq to stay forever, we should have been willing to say so from the beginning. Instead the neo-cons thought we could create a proxy government of US allies, and that the Iraqis would support them precisely because they were "ABBS" (anybody but Saddam). Once they lost momentum, the game was over. All of the rest is simply this administration fighting to avoid facing the truth: they took a gamble, ignoring convential military wisdom about the troop strengths needed, and they lost their bet. Just that simple. It was like sending a couple of cops on bikes into South Central to round up the gangs there. No matter how brave they were, nor how much surprise they enjoyed, it is highly doubtful they could pull it off. That kind of thing only works in the movies.