What sources are there for showing respect and honour to an old person who is not necessarily a talmid chochom or a parent?
מִפְּנֵי שֵׂיבָה תָּקוּם וְהָדַרְתָּ פְּנֵי זָקֵן
והזהרו בזקן ששכח תלמודו מחמת אונסו, דאמרינן: לוחות ושברי לוחות מונחות בארון.
Sefer HaHinuch 257:
And for this reason, Issi Ben Yehuda said in the Gemara (Kiddushin 32b) that even a wicked old man [deserves honor]. That is, one who is not knowledgeable is included in the mitzvah of honoring the elderly, since during his many years he has come to recognize God’s works and His wonders, and therefore he (the zaken) should be honored. And this agrees with what R. Yohanan said, that the law is according to Issi ben Yehuda; “As long as the old person is not a blatant sinner; because if so, he prevents himself from being honored.”