Why do people immediately suspect former abuse when a horse balks at an unfamiliar task, or acts up?

I agree that not every horse that balks has been abused. I have known many horses that have been indulged (one lady I used to know, thought it was y when her horse would spook on the trail and would then complain when he spooked elsewhere.) While there are many awful people out there that do abuse their horses, I think it is not the only cause of a horse acting up. Over indulgence, bad training, mixed up signals, anyone of these can cause a horse to misbehave.