At the end of the day, rally drivers are driving to the absolute limits to get the best times, as a result they sometimes crash. If people are stood in the place they crash, the driver can't be held accountable, you may as well put speed limits where the spectators are standing. If anyone is accountable it is the rally organisers for not ensuring the safety of spectators by only letting them view the rally from safe locations, like their living room in front of the TV.