We can agree that there's always diseases when humans live next to other animals (diseases jump).
That said, "an automotive is preferable to a horse" is a false binary. It assumes that before cars people used horses in similar ways, and that cars are the only alternative to horses.
In actuality, most people walked. Later, most used bicycles or public transportation. Personal vehicles only became popular post-WW2, and they didn't push away only horses.