The reason why it is so very important to highlight this sophistic argumentation tactic is because it has been used so extensively that it is now generally accepted as a legitimate refutation of an individual's argument. Look no further than Bill O'Reilly - a man with a massive tv audience - who constantly is dismissing the ideas or views of someone as far leftist, liberal, Communist, secular progressive, etc. without regard to what the content of their views really are or without answering their arguments, for a case in point.
This tactic is actually the propaganda technique of name-calling:
The name-calling technique links a person, or idea, to a negative symbol. The propagandist who uses this technique hopes that the audience will reject the person or the idea on the basis of the negative symbol, instead of looking at the available evidence.And to help facilitate the effectiveness of this technique we have a line of books that equate liberals with mental disorder, treason, evil, fascism, attacking Christmas, monsters, and such. We have Michelle Malkin incessantly calling people "luny leftists" and "moonbats," Rush Limbaugh and others brandishing the "useless idiots" taunt, and a whole host of others, what former anti-Clinton pundit David Brock has dubbed "the Republican noise machine", which works tirelessly to make "liberal" a dirty word.
The double-danger of this technique is that it has increasingly been coupled with eliminationism. Indeed, the two go hand in hand, since as a group becomes linked to a negative symbol, it becomes easier to advocate their elimination. The more the symbol, with all its negative associations comes to represent the group, the less that the group is perceived as human, the easier it is to rationalize injustice committed towards the group.