There are many reasons why you might want to dismiss what somebody has to say. Some are obvious. They might be biased. Or they may clearly have an agenda. Maybe they are just repeating talking points or propaganda. This is often true of someone who is trying to sell you something whether it is a product or an idea. Sadly, cable news programs seem to be falling into this category more and more these days. To be fair, I should point out that these programs often fall under the category of entertainment rather than news. But, this is hard to detect by simply watching the programs.
Some are less obvious. They might make claims without providing evidence. Or the evidence may be selected to support their view. Anyone who starts with a point of view and looks for evidence is suspect. One should start with evidence and look for an explanation or interpretation. Some people just don’t check their facts or take facts from questionable sources.
Even less obvious problems arise when the issue is stated so vaguely that all the fact checking in the world could not resolve it. For example if someone claims universal health care is good for the country you can pretty much ignore the claim. Almost everyone will have a different idea of what the words “universal”, “healthcare” and “good” means. So, anyone who makes vague claims should be ignored as well.
And anyone who is 100% positive that they are on the right side of an issue should be ignored as well. Any issue worth discussing is too complicated for one to have as simple of an opinion as agreeing with it wholeheartedly.
Next time you encounter someone spewing forth rhetoric of any kind, ask them what the other side of the argument is and how they came to their conclusions. If they fail on either count simply dismiss them as a fool and move on.