0 is a very legitimate number. You can add it to, subtract it from, or multiply it by any other number. Only division by 0 is undefined. However, for a very long time after people understood “ordinary” numbers like 1, 2, or 3, the concept of 0 as a number didn’t exist. Even the Greeks and Romans (apparently) didn’t think of it. Here’s a reference: Earliest recorded use of zero is centuries older than first thought
These days the use of the number 0 is ubiquitous. Computers and cell phones would absolutely not work without it. Even so, some people are a bit suspicious of 0, because it can’t be the divisor of another number.
Nudity is to clothing as 0 is to numbers. It’s clearly a “real” thing – otherwise, how could there be meaningful laws against it?
Just as 0 represents a specific quantity, nudity represents a specific form of attire – just as, for instance, a military uniform does. There might be a little less mistrust of nudity if people could just see the analogy, and form their opinions of nudity in light of that.
And by the way, having 0 of something is not necessarily a bad thing – e. g. if “something” is a disease or a car accident. Likewise, there’s nothing inherently bad about wearing 0 articles of clothing.
Respected authors have recognized nudity as a form of attire. Herman Melville, for instance, in Typee, described the young Polynesian girl Fayaway as clothed in “summer garb of Eden. But how becoming the costume!”