What is up with the person swearing at the taxi in Kim Young-kwang's dashcam footage of retaliatory driving?

There are claims that he sped up because he didn't want to yield,
but looking at the video, it wasn't even the right timing to yield.
It actually looks like it would have been easier to merge in if the taxi had just passed by quickly.
In a case like that, shouldn't the taxi just pass through quickly?