"Having a teacher stand behind you and place his or her hands on your lower back or tug at your hips can be enough to turn some people away from yoga altogether."
Adjustments are a tricky thing.
If I'm about to injure myself, I'm fine with a competent teacher correcting me. Most likely a verbal cue will work, but a hands-on adjustment can, given the right attitude/situation, possibly be helpful.
If I'm doing a pose differently than the instructor, just differently - not wrong, not incorrect - I don't want, nor do I need, an abrupt physical adjustment.
I had an instructor this year who kept telling me to look further over my shoulder, towards the back of the room. I was torquing my neck to its extent. (I took a nasty fall way back in 1987 and my neck has some issues.) So, when this well-intentioned instructor took my head in her hands an wrenched it around, forcing me to "find a more full expression of the pose," I was a bit — well, pissed off.
I have another teacher who seems to believe that he must touch every student at least twice per class. He doesn't make abrupt adjustments. He just places his hands on the body. It's distracting. It takes focus off the practice. I actually have come to anticipate, with a hint of dread, the interruption. If there's nothing to adjust, don't adjust.
If you must adjust, if you feel a compulsion to do that thing, maybe consider the student and ask them if it's okay to make the adjustment. Also, if the student says, "No thank you, I'm good," do not take offense. Please, don't get butt-hurt because the student says, "No, thank you."
I once had a lady offer to adjust a pose for me. (This lady was someone I had met while on vacation. She made it clear that she was a fitness nut, but not in any way a yoga instructor.) She approached me in front of a group of people and said, "Do you want me to fix this pose for you?" I said, "No, thank you." She spent the rest of the day pouting and being generally pissy. This is not cool.
When it comes to adjusting students, I think it's best practice to let the student do their thing. If they're doing something that is harmful, by all means, tell them and offer to help. An instructor in Georgetown once stopped me from attempting a shoulder stand. I was — ego driven — trying to do the same thing everyone in the class was doing, and I had no idea how to do it. I'd never been trained in how to get into a shoulder stand. She was firm, but caring, and I avoided injury thanks to her expert advice. She never touched my body.
Start your class in Child’s Pose or in a seated position with eyes closed, and then offer an option to opt-out of hands-on adjustments by a show of hands. Say something like, “l’ll be offering some hands-on adjustments during class. If, for any reason at all, you prefer not to receive adjustments today, can you please raise your hand? I’ll be mindful to respect your space.”