The Mishna in Rosh Hashana 26a states that according to the Tanna Kama, a shofar may not be made of a cow's horn.
In the Gemara, Ulla states that one reason for this is that "the accuser cannot become the defender," a concept which Rav Chisda had previously used to explain the fact that the Kohen Gadol does not wear the Golden Vestments while doing the parts of the Yom Kippur service which involve entering the Holy of Holies. Since the Golden Calf was made (as the name suggests) of gold, it would be wrong to use gold in this service. So too, says Ulla, since the Golden Calf was (as the name suggests) a statue of a calf, it would be wrong to use a cow's horn for the shofar.
The Gemara on the spot asks why the Kohen Gadol does wear Golden Vestments on other occasions, and answers that the rule of "the accuser cannot become the defender" only applies inside the Holy of Holies. If so, the Gemara asks of itself, what does the rule of "the accuser cannot become the defender" have to do with the shofar of Rosh Hashana, which is blown outside the Holy of Holies? The answer given is that the Torah describes the shofar as being for "remembrance," and this is the equivalent of being inside the Holy of Holies.
About a page later, on 26b , another Mishna teaches that the shofar used in the Beis Hamikdash was partially gold plated. (This point appears to be unanimous amongst all the Tannaim.)
My question is this--how would Ulla explain this Mishna? Why does not the rule of "the accuser does not become the defender" prevent us from decorating the shofar with gold plate, just as it prevents the Kohen Gadol from wearing the Golden Vestments inside the Holy of Holies?