You left out the last lines:
This story has no moral.
This story has no end.
This story only goes to show
That there ain't no good in men.
He was her man, but he was doin' her wrong.
I never agreed with the last verse. Of the four characters (Frankie, Johnny, Nellie Blye, and The Warden) only the Warden didn't cheat or murder anybody. And he's a man. So what the heck?
I have observed since then, that "cheating" always involves two cheaters, one of whom is usually a woman. I have also observed that women sometimes cheat with other women ...