I should start out by saying that I absolutely agree that this isn't an ecological issue. As far as even the local environment is concerned, a scratch on a rock doesn't make a lick of difference. Instead, I think this is about the aesthetic preservation of these routes.
Aesthetic preservation is, literally, a very superficial end, but one that seems to have quite a bit of traction. I would argue that much of the "leave no trace" ethic is based on aesthetic rather than environmental concerns. I'm sure there are various pieces of litter that could be left trailside and remain environmentally inert, their only sin being that they are ugly. I had the same kind of negative reaction to these scratches as I would to that litter. To a certain degree, it's worse because, while I'm no geologist, I suspect that the scratches will remain visible longer than the litter (which may not decompose, but may washed away or covered up).
One argument that I've heard is that the trails themselves are already "scars" on the environment and that this damage is no different. Here is where I must confess the most subjectivity - I just see the scarring as uglier than the trail.
Having hiked this route in the summer, I can certainly understand the need for them in the winter, but without the experience of crampon use, I just wondered what damage was avoidable. From what you write, it sounds like it may be a failure of technology that makes it impractical to prevent the scarring. I think that trekking pole caps are a good solution to possible damage from the poles and wonder if there isn't a similarly workable solution for crampons.
Do you think some kind of quick-release mechanism on the crampons would make their removal more practical? Alternatively, do think that crampons with replaceable, aluminum (presumably non-scarring) tips would be a good alternative? Would the latter still provide the kind of traction needed?