I think any halter could cause pain with enough force applied to it. When using a rope halter you use much less pressure then you would on a nylon halter, so could that really be hurting your horse??
I just got a new gelding last night and still intend to work him in a rope halter (he has horrible ground manners). I'd much rather work him in that than put a chain on him or just get dragged off by him and risk us both getting hurt.
What do you all think about rope halters, or really any type of training halter?