Well, my next door neighbor says her husband is still like this . . .
I think it's such a natural and normal thing for kids to do. Both my kids (girl and boy, 7 and 6) have done it a lot since their diapers were gone, and we just remind them gently that it's fine to do it, everybody does it, but it's to be done in private. They're much better, but they are still in the process of getting the public impulses controlled. They do understand and they are not ashamed, which was my goal. My daughter was relieved to hear that everybody does it.
Especially with my son, people just seem to laugh a little if he does it in public.