Why do we need a pasuk to tell us the din of hamoitzei cilaim bevigdo poshtan- of course you have to take it off - it's not a pikuach nefesh,and this is an issur.Where is there a mekor that kovod habrios should be a factor?
Also, why is the issue "kol mokom sheyesh chilul hashem" and not "kol mokom sheyesh issur deoiraisa"? Why do we discuss "ein cholkim kovod lerav" when what we really mean is "ein cholkim kovod labrios" (unlike the gemoro ineiruvin and sanhedrin where the issue is, indeed, kovod harav)?
1) Good question. Even though normally there is no Hava Aminah to transgress an Isur for any purpose other than Pikuach Nefesh, here we need a verse to teach us that the Isur of Kilayim may not be transgressed for Kavod ha'Bri'os because we find elsewhere that Kavod ha'Bri'os does override some Isurim, namely, an elderly person who finds an Aveidah, and a Mes Mitzvah.
2) You are correct -- "Ein Cholkin Kavod la'Rav" is really not the most appropriate terminology to use here, since the issue is really Kavod ha'Bri'os and not just Kavod ha'Rav. The answer is that the Gemara is borrowing this term of "Kavod la'Rav" from the previous Sugya which discussed Kavod ha'Rav.
Furthermore, we could answer that the verse itself is talking about Kavod ha'Rav, and Kavod ha'Rav does apply to out Sugya. (There is also a Da'as Yachid among the Achronim who learns that the Gemara is talking about when one finds Kilayim on his rebbi.)