Yoga adjustments: good or bad?
This kind of binary view overlooks the value of some forms of valuable touch and doesn't investigate why other forms have little or no value or worse.
1) Directive touch: Indicating the direction of force or stretch in a pose by moving a finger from shoulder to hand or outer hip to foot, for example. This can help a student who isn't understanding a verbal cue clarify what is meant.
2) Strengthening the foundation: Stabilizing a foot or hand that is lifting because of tightness or weakness can illustrate the benefit of good foundation in a pose. Strong foundation in a pose provides better balance and increases the capacity to stretch safely because the muscles are engaged prior to lengthening.
3) Posture deepening adjustment
This is the category of adjusts that is the most contentious, potentially harmful and completely unnecessary, in my view. If a student is being pressed into a pose form because they don't yet have the strength or flexibility to deepen it...that is why they are practicing! Advancements are made through regular practice, not through the application of an outside force. If you practiced piano and your teacher took your fingers and pressed them harder on the keys because you don't have the strength to play louder, it would be ridiculous - because obviously the strength to play louder must come from you, over time, through practice.
This type of adjust can also interfere with an understanding of the specific muscular actions required to accomplish increased depth in a pose (if that is desired by the student). There are instances where the application of force to increase depth in a pose might be helpful as a learning tool to experience what that pose depth can feel like, but this would be a one-time illustration, and the experience of deeper form would probably come safely with time and practice in any case.
Postural yoga practice isn't massage, chiropractic or Reiki. It is a self-practice, often cued verbally by a teacher. That teacher cannot know completely the particularities of your bone structure, or your capacities of flexibility or strength. Through practice, we build our understanding of the above. A teacher can have a conversation with students about their desire for the application of adjustment styles #1 and #2. There really isn't a good reason for #3 and way too many potential downsides.