Despite people insisting on calling tattoos art, there is actually very little that is artistic about them. In most cases they are simply a very basic pattern (similar to wallpaper, though often even less subtle) or crude likenesses of people/animals/plants etc.
Of course these simple representations may have significance for the people adorned in them, but the measure of art is not its symbolic value to a single individual (after all, anything might have such value), but rather its contribution to the refinement of visual expression. In other words, if nobody had ever produced a geometric pattern or crude likeness, then these things might be considered art. Indeed, such likenesses are examples of art when they are found on rock walls painted by stone age people.
But to adorn oneself in these images and then to display them in public is simply to advertise that one's aesthetic sense is no more developed than that of people living tens of thousands of years ago. It demonstrates a total lack of awareness of the development of visual expression, that is, it demonstrates a profound cultural ignorance. It is this (unwitting) flaunting of one's ignorance that earns tattoo wearers such contempt from people with actual knowledge of art.
