"Oh, no, it's outmoding our horses!"

Actually, getting rid of horses in city traffic was viewed by most people as a really good thing.

A lot of period proto-science fiction makes the world of the future horse-free. One article I read in support of automobiles was that a horseless carriage would only be half as long as a carriage & its team, reducing the crush of traffic.

Most especially, getting rid of horses got rid of horse shit. The streets were literally covered in mashed-down manure, and the parish would have the streets scraped down to the cobbles or pavement once a year. "Road dirt" was known to be medically dangerous: any cut or scratch could result in infection or tetanus. One of the planks in the dress reform platform was for women to shorten their skirts & quit dragging road dust into the house.

In 2000 Miles on an Automobile (1904), the author claims horses aren't bothered by them, especially not electrics. What happens, though, is that the horse is walking in front of the wagon while the farmer dozes. The coming of the "road locomotive" startles the farmer who jerks on the reins and makes the horse gib around.

One of the main objections was the speed. A galloping horse was considered dangerous, too.