Board Thread:General Discussion/@comment-27174095-20171114023949/@comment-37250850-20181020181728

DIO was only cautious about punching Joseph because of the fact that Hermit Purple had Hamon infused with it while it was wrapped around him. Only Stands can hurt Stands, and since Hermit Purple was infused with Hamon at the time, it would’ve hurt The World and DIO. If Joseph simply tried punching The World back with a normal Hamon punch, he would’ve died right then and there.