Being in aviation claims, I've seen it go both ways, but if the King Air was unoccupied and the 172 flat out hit it, the liability is pretty clear cut. Even if the KA was dead center in the middle of the taxiway a halfway decent lawyer can make a strong case that it was 100% the fault of the 172. The key fact is that the KA was parked with no crew inside. If the KA insurance company adjusters kick it to the lawyers, the 172 guys should just pay the darn claim and move on, or they'll end up spending more in defending their position with a good chance they'll lose the case anyway. It's a money game, and in the world of insurance, this is no big deal when there are $1,000,000 plus claims happening every day(yes, a simple birdstrike can cost big coin). Plus aviation insurance is a small world. If you try to stick it to a counterpart by not paying, it will catch up to you when the positions are reversed. The best action would be to settle it and move along.