I agree, Rick.

Massive impact for a group that's less than 10% of the users of our trails here in the Sierra Nevada (maybe it's a larger percentage elsewhere - but I'm betting it's still a minority).

Campsites and water sources are regularly fouled, and hiking through miles of horse dung on the more heavily used trails is mightily unpleasant.

It would be nice if they could use waste sacks like the horses in New York are required to wear, with the packers responsible for emptying them out in sites where they will have less wide-ranging impact. The horses will still pee every time they come to a water crossing, but maybe we could contain the solid waste...

Not sure there's an easy answer here. The packers sure fight vehemently for their ability to continue to make a living off of this, and there are places where pack mules and horses are the only cost-effective way to get supplies in to rangers and trail crews (as well as the High Sierra camps, though those are commercial ventures).