I dare you to go outside and say that.
It's common sense, a 50cc engine cannot possibly pollute as much as a 1800cc engine. For some true facts try visiting: http://mysolution.com/MyCar/Subaru360/Emissions
This is a page for the Subaru 360 a small car which used a two-cycle engine.
Please note that Carbon monoxide is well below the legal limit whereas hydrocarbons is far higher that what is allowed legally (in Indiana) because 2-cycle engines burn oil.
Furthermore mopeds use less gas and oil than any automobile which can also help save the environment.
Or were you talking about siezing an engine by using too much oil in the gas- thats a completely different story.