Remember, in an ecosystem, many things are interconnected, and the elimination of one component can spell disaster to some or all of the others.
Maybe the moss is one of these things. Although, some environmental groups should really choose their battles, and this seems (at the surface level) to be fairly insignificant.
We have precluded that we are able to use the earth for our needs, so it makes sense to do that, but as carefully as we can, as if it is destroyed, than we will be too, eventually. Human use of natural resources seems justified, and I feel that some people take environmentalism entirely too far.