Using a training collar (remote collar, prong collar...etc) is like learning how to drive in a driving instructor's car which comes with 2 sets of steering wheels, gas pedals and brakes.
In the beginning the student needs a lot of guidance and feedback and the extra wheel and gas and brake offer the student instant feedback whenever he makes a mistake. This is not possible if it was a normal car and the instructor is only giving the student verbal instruction.
Same with using a training collar on a dog. When the dog pulls, the collar gives the dog an instant feedback and the owner guides the dog back to the right position much like how an instructor uses his steering wheel to steer the car along with the student so the student knows exactly how much to turn and how it feels to make the perfect turn.
Once the student becomes more comfortable and proficient with the tasks the instructor does not need to use his set of tool as much as he used to. When the student has mastered all the tasks the instructor can just sit back. That extra set of tool is now just there as a back up.
This is exactly what happens with training collars. Once the dog has learned how to yield to leash pressure and understands what is expected, correction is seldom required. Eventually, training collars are just there just in case.
The correction the driving instructor gives to the students with his steering wheel when the student commits a mistake will not scare the student and shut her down; it is actually welcomed and appreciated because this valuable feedback can speed up the learning process and can potentially save the student from making a fatal mistake in the future.
The correction a competent dog trainers applies to his dogs is like the feedback the instructor gives to the student. It is valuable and constructive and can save the dog's life.
Some people can learn how to drive without a driving instructor, and some dogs can be trained without any training collar. The point is should you send someone to take lessons if this person cannot learn on his own? Should you use training tools if the dog cannot do it without?
Some instructors are very patient and motivating, while some are very belittling and mean. They use the same steering wheel, pedal, and brake; but can make the student feel very different--one instructor can really make the student want to try and excel while the other could make the student hate driving. The difference lies in the training style--how the instructor communicates with the students and how he uses the tools.
It is the same with dog training. Two trainers with the same tool can produce very different result in a dog.
The key is not the tool, it is the trainer.