This makes a lot of sense. Think of a site like Politico. You would think the country is filled with people who think that either Obama is a Muslim communist, or that George W was a warmongering moron trying to bring about the second coming. Most discussion boards end up devolving into a giant troll pit almost immediately. No matter what the topic, the Fox News and John Stewart crowds go for each others' jugulars, very often with no context to the article they are "commenting" upon.
One of the promises of the Internet was that it could be a town hall, a place where people from a broad swath of geographies and backgrounds could hold discourse in a public forum. Clearly, it hasn't worked out as well as it should have. We have a bunch of morons who aren't looking to debate, but to diatribe. A little nudge here, a little nudge there, and a clever trolling operative could make sure that any serious venue for political discourse quickly descends into rubbish. Troll-fed apathy develops, informed democratic involvement nosedives, which contributes to grid-locked government and a country in decline.
Are all, or even most, of the USA's problems because of foreign trolls? Of course not (plenty of home-grown corruption, poor education, etc.). Nonetheless, it seems like a cost-effective way to undermine democracy, taking advantage of free speech to encourage peoples' worse tendencies.