The basic issue is of communications at an uncontrolled field. DZ or no DZ in the area, you are PIC and it is up to you to scan the area you are flying in. What if these weren't parachutes but rather ultralights.
Same thing can happen and at anywhere in the sky.
Face it guy, you screwed up. Your thing, as a private pilot, is to aviate, navigate, and communicate. See and be seen. If you would have smashed into them, you definately would be violating FARs. If you have a problem with how a DZ runs its skydiving operations I suggest you take it up with them.