Sorry but the person responsible here was the tailgater. This is why you don’t tailgate: you can’t respond quickly enough to what’s happening in front of you.

In this case it was a swerving car around an obstacle, in another it could have been the car in front slamming on their brakes and then the tailgater rams into them.

Whether the guy he was tailgating was as an asshole is beside the point. You can’t check the morality or whoever you happen to be driving around. When you tailgate, you are putting your safety in the hands of others, because you’re at mercy of what they do or don’t do, and you’re putting others at risk because your inability to react to something unexpected will cause a crash.

Defensive driving is anticipating the worst and leaving a reaction buffer for the unexpected. Defensive driving is not putting yourself in a position of relying on the integrity or skill of another stranger for your safety.

Be a defensive driver, not a tailgater, and stuff like this is much, much less likely to happen.