ivwshane -- That thread is indeed the perfect example and was the most proximate motivation for posting this thread. But it's an issue that comes up a lot. So much so that I asked for one of the rules of this place to specifically address the matter. Thus, I thought it worth discussing here to explain my views and hash things out a bit.
As I asked were the statements false? That wasn't a "gotcha" question, I don't know myself. It seems that the correctness of the statements are the real test. If it's a lie then you have a legitimate basis to attack the source, but if one doesn't check then consider the possibility of a personal bias. Attacking without verifying isn't the best logical response.
The problem here is that you are engaging in reversal of burden.
When an article makes claims or presents statistics as factual, the burden is on the author, or the presenter of the article, to provide adequate substantiation for those claims or statistics. It is not the responsibility of those reading the article to disprove its claims, until and unless a reasonable job has been done in proving them in the first place.
When an article does not provide that backing, then its entire value rests solely on the credibility of the author. That credibility has to be assessed because there is nothing else behind the claims other than the author's personal viewpoint.
Now, it is certainly possible that an argument can be well made by someone without providing backup for his or her claims. But people have to decide whether it is worth even taking the time to respond based on the likelihood that the claims are accurate. This again comes down to the credibility of the author.
As an example, if I read an article making all sorts of claims about how fast food is really healthful, and the article doesn't provide scientific backing for what it says, I will assess it very differently if it is written by a registered nutritionist with 20 years of experience, or if it's written by a VP of public relations for a hamburger chain. If the nutritionist wrote it and I disagree with the claims, then it might be worth my while to try to counter-argue them. If it was written by a PR flack, I'm not going to bother.
And it's even worse on political topics. As I said in my initial post, an article on guns written by Sarah Brady
or Wayne LaPierre better be well-backed or I'm not even going to consider it.