The honest consideration of other viewpoints is an ethical duty if you are a persuasive speaker seeking to convince the audience of something you believe to be true. You may be making the wrong conclusion based on the evidence or your evidence may be flawed, both of which can be shown by examining other views. Perhaps you and your opponent are using the same evidence but come to different conclusions . If you are able to consider other viewpoints and still believe in your original view, then you are ethically able to attempt to persuade others.
Chilean Presidential Debate
Political debates highlight how two people can interpret the same evidence different ways and come to opposing views.
As a persuasive speaker, there is always an incentive to invent, or even just fudge evidence so as to strengthen your appeal and weaken opposing viewpoints. However, this is akin to lying, and clearly unethical.
Furthermore, evidence must generally be accepted only after intense scrutiny. Statistics, and many types of evidence, do not fall neatly into the category of "true" or "false. " While there are some undeniable truths, such as the fact that the earth is round, there are many more that fall into a gray area. This is due to the fact that evidence comes from a process which may be flawed. When the process is flawed, there may be a statistical fallacy. For example, if a survey asks skewed questions, the results may not reflect the truth. Though many researches, scientists, pollsters, and investigators do their best to avoid fallacies, the possibility always exists that one may be proven.
Since it is very easy to unintentionally lie by not explaining all the nuances of the evidence and it is very easy to use evidence that may contain fallacies, it is the duty of every speaker to consider the viability of opposing viewpoints before rejecting them. It is your ethical duty to allow others to criticize your viewpoints because if your argument is truly sound and you are truly making the appeal to convince the audience of something that you believe to be true based on all the evidence, then your evidence should be able to withstand the scrutiny.