Re: Human space travel a cancer in the universe?
Back when I attended a lot more space conventions, I was always running across people who thought we would "ruin" space if we went out there. There are people worried about us ruining the "environment" of the Moon, by which I assume they mean we will take the existing visual arrangement of dead rock and change it to a different arrangement of dead rock.
Another favorite were those people against nuclear propulsion in deep space because the radiation would "pollute" the solar system.
Such people are best ignored.