To be fair, as someone not living in a tumbleweed part of the continent, once those tumbleweeds start getting bigger than a basketball, it does look pretty alarming, as though they're some kind of animal you can't avoid hitting.
Also, tumbleweed aren't sagebrush. The boyfriend/husband/whatever knows nothing of botany.
One time I was driving across Texas and out of nowhere came a tumblweed that had to have been 5-6 feet tall. It didn't have a "stem" so much as a *trunk*. And it hit my side mirror and destroyed it.