Defending the honor of a parent- Protesting someone who defames one’s parent and defending their honor:
It is a mitzvah on one who hears a person defaming his parent to protest against him, and to defend his parents from the libel telling the person that he is stating a lie about his parent. A child does not have the right to forgive his parents honor in these matters. Nonetheless, he is not to hit the person who defamed his parent. Likewise, he should answer him appropriately and honestly and not make up a libel in return. Furthermore, if one knows that by protesting the defamation it’ll cause it to be spread even more, then it is permitted for him to remain quiet.
Not to act in a way that will cause people to curse one’s parents: Included within the mitzvah to honor one’s parents, is to abstain from behaviors that will ignite people to belittle one’s parents.
 Pesakim Uteshuvos 240:24; Encyclopedia Talmudit Erech Kibud Av Vaeim Vol. 26 p. 390-391
 Sefer Hayirah of Rabbeinu Yona 197; Sefer Chassidim 72; See Orchos Chaim of Rosh 82
 Yam Shel Shlomo Bava Kama 8:50; Shut Maharshal 101; Shiyurei Kneses Hagedola Y.D. 240:5; See Bereishis 50:25; Sotah 13b; Encyclopedia Talmudit Erech Kibud Av Vaeim Vol. 26 p. 390
 Sefer Hayirah ibid; Orchos Chaim ibid
 Sefer Chassidim ibid
 Sefer Hayirah ibid; See Minchas Elazar 4:13
 Sefer Chareidim 66:77