Touching a stranger, even accidentally, is considered rude. The six inch rule states that one should keep a distance of at least 6 inches to prevent unwanted physical contact. That’s a good rule for the race track too.
The mirror-to-mirror contact was socially rude and the spark that ignited the incident that followed. Was it payback? Were the drivers simply flustered from the previous contact? It doesn’t really matter. You and everyone around you has a right to a reasonable amount of racing room. How much room depends on the skill and mutual trust among the drivers. If you’re in a race with drivers you don’t trust, leave a half a car of room (but not a whole car because that’s an invitation).
Both drivers share some blame because both drivers could have prevented the incident. The slower car should have seen the faster car and given it room. But it’s always the responsibility of the faster car to make a safe pass. The racing line drifts out to the left here, and there wasn’t much room to pass safely. Before you attempt to pass another car, ask yourself “is this how I would pass a team mate?” Unless the answer is an emphatic ‘yes’, find another opportunity.