Gemara:It is forbidden to spit on Har Habayit (the Temple Mount) by comparison to shoes: If regarding shoes, which is not a matter of disgrace, the Torah says: "Remove your shoes from your feet," spitting which is considered a matter of disgrace, all the more so that is forbidden in a holy place.

Ein Ayah:One of the expected results of the sanctity of the Temple is that when one stands there, he is to be totally dedicated to the service of the Holy and the intellectual, and thus not prepared to be involved in the needs of the body. For this reason, he is required to remove his shoes before coming to the holy place, as wearing shoes is a sign of being ready to take care of mundane needs. The connection between shoes and a person’s needs finds expression in the fact that the morning blessing of "… that He did for me all my needs" is recited when one puts on his shoes.
If one needs to refrain from the needs of the body, even when they are not intrinsically matters of disgrace, certainly he has to refrain from that which is unseemly, whether it is categorized as such based on convention, based on nature, or morally, as the example of spitting represents.