I think the issue here is that this is a rider who came for help because she doesn't know how to stop her horse...if she doesn't know how to handle that situation, do you honestly beleive that throwing a bigger bit in the horses mouth and saying to the rider "now PULL HARD" when he doesn't stop is actually going to help? Yes, for alot of people with training experience, we know how to use our tools, but for an amature rider who is looking for help? Probably not; what would likely happen is the rider pulls, the horse wigs out, stops hard, and possibly goes over because the release isn't immediate; or goes over anyway, because the new bit is such a surprise. Another possibility is the horse simply flips his head in the air, because he doesn't understand the concept of the new bit, and keeps running, only now he is running blind because he is confused and frustrated; rider keeps pulling, possibly starts jerking the reins, horse eventually pops rider in head, because he freaks out all the more. I've seen these things happen more than once in my years of training horses; and often by reputable trainers...and what winds up happening to the horse? He's coined as untrainable or dangerous...but it didn't have to be that way.
I DO NOT think that introducing a horse to a new bit should ever be taken lightly, or done just as a quick answer, because the horse has an obvious problem in his training.
I AM NOT against curb bits, but I'm not for them when they are suggested to be used in a situation as is suggested. There is more work that needs to be done than a harder bit put in the horse's mouth, and it won't get accomplished by suddenly suprising the horse with a bit with more leverage and bite.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."