The 11th Commandment for liberals seems to be, “Thou shalt not intervene out of self-interest.” Intervening in civil wars for humanitarian reasons is OK, but meddling for national security reasons is not. This would explain why liberals supported interventions in civil wars in Yugoslavia and Somalia but think being in one in Iraq is the height of folly. If only someone had thought of labeling the Korean conflict a humanitarian intervention back then, we might not face the horror and the danger from North Korea today.
Goldberg’s thesis is easily disproved by looking at Afghanistan. The invasion there was clearly in the national interest, and clearly not a humanitarian issue. Liberals supported the invasion then, as did everyone. Liberals have not reneged on their support. Afghanistan has never been a contentious issue, precisely because that war was so clearly in the national interest.
(This is slightly edited from the comment I left there.)