It's unavoidable really - it's nigh on impossible to consistently and fairly assign blame using an automated system. Hell, race stewards in real life frequently struggle to figure out who's responsible for a crash. However it should even itself out - say you're in a race of 16 cars and one of them is a crasher. He hits you - you both get a 'penalty point' (just an example, no idea how the actual scoring works). During the course of the race he manages to crash into everyone else once too. End result - he has 15 'points', everyone else has 1 each assuming the race is otherwise clean.
Soon enough, assuming you're picking races at your rating, you'll never see that person again unless they improve, you can drive safely with your new buddies, and your safety rating will recover from the slight hit it took initially. Of course if you just dive into random lobbies with no rating restrictions, then you're taking a risk, but that's kind of outside the scope of this system - the whole idea is you use the system to help you find clean races.
