How does a circumstantial ad hominem argument accuse a speaker of hypocrisy?

A circumstantial ad hominem argument accuses a speaker of hypocrisy by highlighting an inconsistency between the person’s own actions or circumstances and the position they are advocating.1

Rather than engaging with the substance, facts, or logical validity of an argument, this approach attempts to discredit the speaker by pointing out that their behavior contradicts their stated claims. For example, if a person who smokes cigarettes argues that tobacco consumption is unhealthy, a circumstantial ad hominem attack might dismiss that argument solely by citing the speaker's own smoking habit.1

While this tactic is often used to undermine a speaker's credibility, it is considered a fallacy when the speaker's personal inconsistency is irrelevant to the truth or logical soundness of the argument itself. By focusing on the perceived hypocrisy of the individual, the attacker avoids addressing the actual merits of the claim.1