Your response cracked me up. actually, I'll admit, I sort of agree with both of you. Here's some detail, about my opinion on the matter(s), it's more complex than you indicated in your initial post.
Less parts, easily repairable with simple, somewhat inexpensive parts. The less "manufacturing" that needs to happen, "Pre-consumer" in less energy consumption.
for Example, my TOMOS has less 'manufacturing' than a new Lexus. Before you've even bought it, it has consumed a TON of resources.
riding a machine with pedals is good for the environment. This is my 'philosophical' point of view. Even if you never actually pedal your moped anywhere, the fact that it has pedals will make some people think "Alternate" which may have a "trickle-down" effect and make people look at solar or wind, even if they don't actually get a moped.
Mopeds do not have, consume, or use up batteries, generally speaking. Lead acid batteries are a huge environmental issue. cars go through several in their life span.
Mopeds use less gas, and take up less parking--this reduces the area which needs to be ruined with paving, cement and asphalt. Something like 10% of our country is 'paved'. It costs money and miles of 'blacktop' must contribute to global warming (which is happening with or without human help anyway)
volume of fluid. Most people think of comparing a "perfectly tuned" brand new vehicle vs. a brand new "perfectly tuned" moped. I also like to consider older vehicles. An SUV that has fallen into disrepair and is leaking coolant, transmission fluid, or oil, or brake fluid. Let's assume this vehicle has a "real bad day" It blows a brake line and overheats (because all your oil and transmission fluid has leaked out...) worst case scenario, this crappy SUV has just dumped several gallons of toxic chemicals where they will probably flow into a storm drain.
If you don't think things like that happen, you've never tried to keep a 400$ car running for four or five years.
Now, on the other hand, your moped has TOTAL TERMINAL SYSTEM FAILURE---You might leave a mess, but nowhere near the pollution potential of a larger vehicle that is breaking down.
But, there is no question that moped exhaust contains lots of bad things, and it's a FACT that moped exhaust is worse than a tuned up car. That seems to have been Ryans main point, and I think he's missing the larger picture. We've talked a lot about this here before, and I think we (all the regulars) agree that moped exhaust is nasty stuff.