[kipqi]

Using != abusing. Camping in a public space means taking part of it for yourself, permanently. In other words, you're taking away the right of the rest of citizens of using that part of public space.

Defecating is a public health issue, too.

[ravenstine]

Exactly. People defecate in the woods all the time, but they have the decency to at least dig a hole and cover it. Just because it's natural to take a shit doesn't mean we should be stepping in it.

[CydeWeys]

Even shitting in the woods isn't great, it's just that most people won't use the better but grosser alternative (shitting in a sealable bag).

In parks where restrooms are provided, like the Grand Canyon, shitting outside of restrooms isn't allowed. Anywhere the foot traffic gets high enough, the park service will put in restrooms and require people to use them to defecate, because the alternative is pretty bad. Even in the wilderness.