I have to say, people can be stupid. As for litter, smog and raw sewage in water ways - people just damage their own way of life when they eject these things into their environment.
I however do not believe that we are doing permanent harm to the planet. I believe in being energy efficient because it conserves resources and reduces my cost of living. I am in the beginning of a project to convert my house to run from micro-hydro electricity. I compost my scraps and paper. I use bat guano to add to my compost to keep the paper from diluting the potency. I raise a garden and try to do for myself and family as much as I can to be self sufficient. - - - but I don't cringe when I drive my full sized pick-up-truck.
I think that we could do the planet more good and improve the cleanliness and reserve of resources if people were educated about the greater quality of life they could experience if they lived responsibly, recycled as much of their waste as possible, reduced consumption of natural resources (reduces cost of living) and became more self-sufficient. It just gives one more of a sense of life being right.
Being Green is often a luxury only we can afford. My town wants $20.00 to dispose of old comps and monitors and they just ship them to third world countries so little kids can burn the plastic of the wire to make 20 cents a day. Just sending a toxic problem to countries that can't say no.
$20.00 is a lot of money and accounts for the amount of %&$* that gets dumped on the roadside..
The proposed wind farm on Cape Cod is a perfect example of people being people. There was as much resistance to a wind farm as there would have been to an oil well...