It's a form of bullying meant to "own the libs" through harrassment. Some people love it, and it strengthens and encourages them to see it because it reinforces their tribal narrative. Others hate it, and they'll be further entrenched in their tribal narrative. It's divisive, plain and simple. Score one for polarization and infighting.

It bears mentioning that this is a highly vocal/visible, tiny minority. They serve to poison the well. Folks on the left are inclined to point at this bullshit and call folks on the right idiots; the vast majority of folks on the right are like "I'd never do that."

On the other hand, this small minority is numerous enough that every Prius owner I've known in Texas complains about this. In their frustration, it's easy to see why they'd paint with a broad brush.