Heterosexuals, especially heterosexual men, have an intense fear of the penis. They don't want to see it, they don't want to think about it. They design costumes that hide it as much as possible, and when that's impossible, they pretend desperately not to notice it.
So frontal nudity in a tv program or movie gets it a "mature audiences only" rating, and public nudity will get you registered as a sex offender for life.There is an exception, however, for artistic depictions, paintings, drawings, and statues. Some blue noses still complain, but in general a depiction of a nude male is fine.
T.S. Eliot used one for the cover of one of his books.
And Maurice Sendak, for his illustration of Melville. This guy looks like a grown-up version of Max from Where the Wild Things Are.
"The Source of Power," by German sculptor Arthur Lange, about naked men holding hands.
Danish sculptor Bertel Thorvaldsen displayed full frontal nudity in many of his statues, such as Adonis.
Even Thomas Hart Benton, the great muralist of the Jazz Age, presented an outline of a penis.
If your art is too naturalistic, so it looks like a photograph, you'd still be wise to throw in a fig leaf.
And arousal is strictly forbidden.