I think the OP needs to lighten up a little. He appears to presuppose that humans are not part of the natural environment. Moving scree and changing the erosion patterns is not "damaging" the environment, it is simply interacting with it, and I believe we all get to do that. Even if the ski-scree tracks are visible for years that does not necessarily constitute a negative change in the natural world. Why is it that every animal in the world gets to poop whenever and wherever they want, but somehow when humans do it in the wilderness it is viewed as pollution? I am certainly not in favor of raping the countryside, but these guys aren't exactly strip mining, they are simply using the natural world in a rather unique way. Is the "environment" a better place if we all stay home and cease interacting with it? When is interaction positive, neutral or negative, or is there even a distinction?
The OP states "I am angry because this will cause damage to the environment through erosion." Erosion is a natural process that we are all part of. Every step and breath you take has an impact on the environment, and arbitrarily deciding which impacts are "negative" is a rather futile endeavor. It is good to have rules for things like pooping, and keeping vehicles and hikers on trails to preserve the natural landscape in high use areas, but denying folks the freedom to move a little scree around in the name of fun is not going to save the planet from ruin by erosion. It looks pretty dangerous, so the video shows natural selection at work.