I agree and it really pisses me off that they allow corporate grazing, but not bicycles. And, horses and pack animals. There is no difference between horses and bikes. Well it can be argued that bikes are easier on the trails (plus we poop less).
You know, at the risk of pissing you off Mud, I gotta say that I agree, I disagree, and I disagree.
1. I agree about cows. There is no justification that works for grazing cows in federal wilderness. Grazing was shoehorned into the law in 1964, but it's long outlived any usefulness it had. Plus the corporate welfare types who do it pay anywhere from 1/4 to 1/10 of what they'd have to pay for similar grazing on private land. It's a giveaway and it's wrong.
2. Although I used to agree with your comments about horses, I've changed my mind over the last decade. Here's why:
Over the last 40 years, it seems to me, we've gotten to a state in which fewer and fewer young people use the wilderness. Now, maybe I'm wrong, maybe I just see fewer young people using it. But I don't think I'm wrong, and it scares me.
It scares me because the less people know the wilderness, the less they will stand up for it. Ed Abbey said this succinctly: "The concept of wilderness needs no defense, it only needs more defenders."
Unfortunately citizens of this country all get to vote, whether they value the environment or not. They even let people vote who might want to put new tungsten mines (or some such) in wild and protected country.
Horses actually help with this issue, they help "create defenders." Many people are being brought into (and shown the value of) wilderness by horses. That is, horses are to some extent making wilderness defenders out of people who might not otherwise care. There is value in getting people out there (even fat, budweiser swilling horse-packer clients - who are not the majority mind you as far as I can see - can be shown the value of wilderness). This way of looking at this issue led to me becoming more understanding of horses and horse packers (and more willing to put up with their crap, and all of their negatives).
3. And I strongly disagree with you about bikes in the wilderness. The vast majority of hikers find that bikes seriously degrade their wilderness experience (the Wilderness Act itself talks about primitive, non-mechanized recreation; there's a lot of value in this type of experience).
Although most bikers don't see this, the degradation of a hiker's primitive, non mechanized recreation by bikes in the wilderness is very, very much like what bikers themselves would experience if they were "forced" to share their trails with motorcycles and ATVs (open Henry Coe to motorcycles!!). Would any sane mountain biker enjoy sharing a trail with motorized, off road vehicles? Hell no, it flat ruins the experience. It's no different for hikers, no different at all.
Would you as a biker want non-motorized bike trails opened up for motorized use? Should all trails everywhere be opened for any type of travel? Should the lowest common denominator prevail? Or should different values be accorded respect and protection in different areas?
And if you don't believe my comment that bikes seriously degrade hikers' wilderness experience, check into it for yourself. Try some of the PCT Association blogs and/or just backpacking web forum discussions. Bikers frequently flaunt the law in Southern California in particular; they ride wherever and whenever they please. It's a big problem in the eyes of foot travelers and you'll see it in these blogs and forums.
Oh, and I absolutely do agree with your comment about the relative trail impact of horse versus bicycle use: horses clearly have more impact than bikes. But that's not at all the issue, that's not what's led to mechanized travel restrictions in wilderness.