As explained in your textbook, public speakers have an ethical obligation to avoid name-calling and other forms of abusive language because such language ...

e) b and c only

Explanation:

Public speakers are ethically obliged to avoid abusive language because it demeans the dignity of the groups or individuals being attacked and undermines the right of all groups in the U. S. to express their ideas.

In public speaking, any kind of name-calling is ethically wrong. Speaker must avoid racist, sexist, chauvinistic remarks and names, and any other kind of abusive language that is considered politically incorrect. The language of that kind devalues people and reduces them to the stereotypes.

By publically voicing these opinions, a person encourages and reinforces prejudice, hate crime, and civil rights violation, which is not just a problem of disrespect but also a destructive social force.

Finally, in US society all people and groups have a right to speech, and an abusive language is often a tool of silencing. As a part of the US democratic society, the public speaker has the obligation to avoid these tactics and let each group and individual express themselves without harassment.