There is nothing about nudity in itself that magically turns people into sex objects. But nudity in the arts is a complex subject. There are instances in which an artist has used nudity to titillate his or her audience, which is almost synonymous with turning someone into a sex object. Hollywood is famous for using nudity in that manner.
But Hollywood aside, nudity is quite often used in the arts in ways that are not meant to reduce the nude person to a sex object. Most often, it seems to be used simply to invoke some feeling or appreciation for the beauty of the human form.
But in other instances it has far more complex missions, such as to symbolically suggest something about an ideal or concept represented by the nude person. For instance, there was a period in American arts when it was almost commonplace to represent truth as a nude woman in order to suggest that "Truth is naked and unadorned", or some similar idea.