In short, a speaker's appeal to the audiences "ethical" side can be an appeal to the audience's:

A. Ethos

B. Logos

C. Pathos

A. Ethos

To properly incorporate ethos, a speaker needs to show that they are taking care of the audience ethically, showing that they are responsible and credible about the topic. This can include their experience and credentials as proof that they will be presenting an ethical overview of the topic.