Admittedly, what is truth and what is worthy are difficult things to know. But if this is not appreciated by a persuader, it could indicate he has taken an easy path to his position. It shows he may not have carefully analyzed his assertions. It is not likely he has open-mindedly compared his ideas to other viewpoints. The listener should thus question his information.
Most groups demand some degree of allegiance of their members.
Knowing the agenda of any groups with which a speaker affiliates herself is helpful. It's hard to know without finding out. The selling of environmental backlash. Logical reasoning in natural language.