Congressmen who willfully take actions during wartime that damage morale and undermine the military are saboteurs and should be arrested, exiled, or hanged.
The quote was easily proved a fraud, and there's no point in adding to the history of its provenance, which you'll find here.
But the remark should have raised eyebrows to anyone with a passing knowledge of American history: after all, it was Lincoln himself who, while in Congress, voted to end the Mexican American War.
What seems to have received no attention is another suspicious aspect of the quote, pointed out to me by a coworker and confirmed by our inhouse facsimile of the original OED. The problem is the word saboteurs. Lincoln could not or would not have used this term. Although coined by the French in the early nineteenth century, its use in English dates only to the era of the Wobblies (the OED's first citation is from 1918).
It's almost as if somebody were trying to sabotage the quote itself.
Update: Finally, the Washington Times not only corrected the article, they removed it--more than two days after it was posted and only after enduring ridicule by a number of newspaper articles and news programs and after Gaffney was humiliated by Glenn Greenwald on the Alan Colmes Show.