Earlier quoted context omitted.
STDs are hardly propaganda, and promiscuity does indeed increase the risk. Besides she was clearly a troubled youth, with sexual abuse home and her further abusive relationships conveyed early in the movie.
Major Dan was getting it on with prostitutes but he doesn't get aids. It also showed the anti war guy just happens to be a women beater...
I also thought it was great how they handle the subject in that movie. And what about Forest who loves Jenny regardless anything on her past?