The word "shameless" is often used in a pejorative manner, e.g. "he was a shameless opportunist." But it can have a less judgmental albeit less common use to mean someone who is bold and not hindered by petty morals.
The bloke below is hot and horny and ready for action so he's shamelessly showing his goods. This is one of my favorite amateur sets because you can really read the unbridled lust in his face. He needs satisfaction and he needs it now.
See, shameless can be a good thing, too. Was this a teaching moment?