The internal structures of our penis have become accustomed to hanging large amounts of weight yes. When you body build you are also becoming accustomed to progressively increasing the load over time.
However.
Through bodybuilding, you are damaging type I and type II muscle fibers through a strong CONTRACTION of those muscles. This of course leads to many things, a strong metabolic response which signals your body to flood with large amounts of naturally occurring anabolic hormones, then you get out of the gym and feed yourself so that these nutrients can allow for an anabolic environment. If properly utilized the naturally occurring results of this type of stimulation will lead to growth VIA hypertrophy and/or hyperplasia.
This my friend is a completely different response you are attempting to attain by hanging a weight off your most sensitive organ. When you are hanging a weight, there is no contraction. You are not attempting growth through the same pathways. Essentially you are attempting to DEFORM the tissues, smooth muscle, ligaments, etc in your penis through forced damage. The natural reaction of this on your body is of course to become stronger and harder so that these forces dont rip your dick off next time you do this.
Do you think your body says “OHHHHH thats what this asshole is trying to do…just make my dick longer…ohhhh ok here ill let it grow really quick for him”? The answer is no. Your body is saying “What the fuck? Dude something is trying to rip my most precious organ off my body, I better make it harder and stronger so this shit wont happen!”. Its biology my friend, our body is adapting to survive. And when your body is adapting to the hanging stress, I can assure you that it is not growing via hypertrophy or hyperplasia because of proper stimulation, nutrition, and recovery, or through the activation of new satellite cells. It is callousing, just like when you lift and you get those callouses on your palms so that the bar doesn’t rip through your hand.
Use your head. If something is not working for you, TRY SOMETHING NEW. The definition of insanity is trying the same thing over and over and expecting different results. You can thank albert einstein for that one.
Be gentle. Take it easy. Be nice to yourself, your body will thank you.