An Ad Hominem attack is only valid when a person is using opinion and or circular logic in an argument. When facts cannot be substantiated or are outright ignored to enforce one's opinion on an issue, an Ad hominem attack is justified because when the facts are ignored the issue at hand is not as important as the perpetrator's ego and their expression of being proven right.
A valid argument is based on verifiable facts and ignoring those facts in order to win an argument by anyone changes the outcome of the argument because the importances of the issues and/or premisesare subjugated to the ego of the perpetrator.
As long as the Ad hominem attack is not abusive or circumstantial, it can identify the weakness of the perpetrator’s argument. However, if the perpetrator relents and dismisses their egotistical agenda and comes back to the issues and facts of the initial argument, then, and only then, can the argument reflect experience and not opinion.
For example, many political pundits attack an opponent based on partial truths that can be spun into a ‘possibility’ of them acting a certain way in the future. This is nothing more than sheer speculation based on converting possibilities in probabilities associated with past behaviors. There is no certainty here, just speculation.
However, if the proponent is charismatic enough, the sheer emotional
Logic is not the sole progenitor of truth. Intuition must be juxtaposed with logic in order to arrive at a viable conclusion concerning the facts. Logic identifies what is readily apparent and intuition identifies what is not readily apparent. Use both systems to identify and validate the truth.
Generally speaking it is never good to attack the messenger of an issue or a fact; however, when their facts have progressed into opinions that skew the initial facts, making them aware of it can only come from identifying their perceived attempt to control the argument. Some things cannot be proven by logic and should be debated in the realm of individual understanding and not collective reason. ~Dean A. Banks, D.D. (Spirituality Guidance Channel)