Well it doesn't. Many liberals don't care about argument ... they don't even care about rhetoric. All they care about is demagogy:
http://en.wikipedia.org/wiki/DemagogyWikipedia describes a demagogy as "a political strategy for obtaining and gaining political power by appealing to the popular prejudices, fears and expectations of the public — typically via impassioned rhetoric and propaganda, and often using nationalist or populist themes"
Some socialists have the decency to be ideologues - you may agree/disagree but at least they have a consistent worldview.
However, many liberals are demagogues (remember Unfairenheit 911?) and rather than propose a consistent set of values, all they care about is dismantling mainstream conservative values.
Ironically, when we are talking about ordinary people, conservative values can cut across political boundaries.
For example, the blue collar worker who joined the union to protect his job, may also be working hard to support his family. He may believe in law and order, and as a hard working citizen may hate the way the liberal elites are soft on crime. He saves up to take his family on vacation once a year, and enters into saving schemes so that he can give them a decent Christmas.
And he would NEVER dream of giving someone a HAPPY HOLIDAYS card ...