In terms of commercial fleets (be they cars or commercial trucks) drivers are held accountable for accidents. There are 2 types of accidents: Preventable and Non-preventable.
A non preventable accident is one in which there was NO ACTION the driver could have taken to prevent the accident from occurring.
You hit a parked vehicle, the accident was preventable, you are at fault. The other driver could be ticketed for parking illegally but that does not mean others can play demolition derby on his vehicle with no consequences.
You are still required to operate your vehicle safely and without causing injury or damage to property. You failed to do so, you are at fault.
Let me guess - Since you posted this on Sunday - You were leaving a bar or party, had a few too many to drink, your abilities were impaired and you think this is your "out"? Nice try. Just man-up, pay-up, admit your fock-up, and drive a little more carefully in the future.
Here endeth the lesson.