I race from the back in lower DR and see this behavior in nearly every race. I always race at S99 but pass on average 7 people per race so get a good view of what goes on during the race. I avoid people like this most of the time but sometimes, like there, there's not much I can do. The penalty system gets these cases mostly right, but as you see, if the other car drives off, you are screwed.
Sorry, the penalty system is bad. Otherwise it wouldn't be so hard to get the clean race bonus. I drive very carefully and go off track maybe 1 in 20+ races, go out of my way not to hit anyone, back out often, make room for cars that want to pass badly and only make a pass I'm 100% sure about. Yet only manage to get the CRB in 1 of 4 races on Interlagos because of all the bumping, punting, barge passing from behind.
Sure we have to be responsible for out own actions, yet keeping quiet when the penalty system would be improved if replaced by a coin toss, is just as bad imo. Atm I'm all for shared blame, any contact, both cars 5 seconds penalty. Heck, bring it back to 10 sec for any contact like it was for a little while. Races cleaned up considerably since there was no way to get away with any contact passes.