If you don't believe that an anti-US fifth column (8-10% of the US population) exists in America, read these voluntarily written articles from some very well-known blogs. Anyone, Democrat or Republican, Liberal or Conservative, who feels any love for the United States, will be offended by this :
Daily Kos, The Left Coaster, Daily Kos again, the burning of US soldiers in effigy, the comments here, this poll stating that 11% are hoping for America to lose in Iraq, and Rosie O'Donnell defending 9/11 mastermind and Al-Qaeda No. 3 Khalid Sheikh Mohammad on national TV (even though he also confessed to making plans to assassinate Jimmy Carter and Bill Clinton). Even Glenn Reynolds of Instapundit, as genuine of a political moderate as one can ever hope to find, has arrived at a similar conclusion, going even further than me by saying the 'left' sides with America's enemies, as has Captain Ed. I don't think the fifth column represents all of the 'left', however.
There is a significant percentage of the US population that does not want the US to win in Iraq (and will deny the existence of victory when we achieve it by 2008). Some because they have always hated America (fifth-columnists), others simply because they hate President Bush so much, beyond any policy disagreement, that they want to discredit him even if it means harming America (Bush Derangement Syndrome), and yet others because it is a socially fashionable opinion to hold, and they need to conform to the groupthink of their clique (fashion sheep).
This is an article I could have written a long time ago. I refrained in order to wait until the anti-US fifth column overplays their hand, which has happened. Applying true Sun-Tzu tactics, their exhausted state is the perfect time for a counterattack.
You can win debates against all of them easily, by debating them on principle, which they are usually not confronted on, and observing their willingness to offer constructive ideas.
Also, never refer to these people as 'liberals', 'progressives', and 'elites'. This is not only an insult to genuine classical liberals (who have an open mind and can come to agreement with others easily), but these are terms that the actions of anti-Americans are quite the opposite of. Does it make much sense to debate someone if, from the start, they insist that you address them as the smarter person among the two of you, without them having to earn that status through deeds? So don't allow them to stealthily get away with this branding over here.
Here are some examples of common one-liners (in italics) and possible responses you could wield (in bold) :
And he goes on to make the points that, if lefties could be swayed by logic, would shut them up.