It is all a matter of managing stock and backpacker use- a balance. Many of the less used non-maintained trails would disappear if not for occasional horse use. On the JMT, I would say that backpackers do more damage simply because they probably outnumber horses by 100 to 1. If managed properly horses have their place in the wilderness, including the high Sierra. There are environmentally conscious packers and slobs, just like backpackers. A good packer does not want to ruin the trail anymore than we do. After all, they have to use that trail again too.

Emigrant Wilderness (where balzaccom does most of his backpacking) does have heavier horse use than most of the Sierra, because it is one of the few wilderness areas that remain friendly to horse packers (regulation wise). The horse people are legitimate wilderness users too, and some areas have to be left for them to use.

I agree that if all you want to do is have an animal carry your gear, llamas or goats are great. Some areas do not allow goats because of potential cross-species disease transmission to mountain sheep.

I have a very good friend who has had a family pack business for over 40 years and know many who have their own horses who use the wilderness. I have used commercial packers for spot resupplies and when my children were young I would have a commercial packer take us in (uphill), and we would slowly amble out (downhill).

I would say that about 70% of the time I have no problem with horse use or packers. There are times where I have seen lots of damage, particularly at large established campsites. I think you can get a skewed view because you really remember the badly damaged sites, and forget all the remaining area that is not damaged.