No, it is often not true. An increase in demand can be very destructive socially, morally, or in human costs.
An increase in guns means an increase in fear and insecurity. In private hands, it means an increase in murders. In government hands, it means an increase in war is likely going on, about to happen, or feared to happen. Either way, it means a loss of resources that could be devoted to almost anything that would be better, such as education, infrastructure, and so on.
An increase in alcohol or other drugs likely means an increase in human misery, overdoses, early deaths, and crime. An increase in pornography could be positive in the sense of less censorship or taboos on talking about sex, but it likely is negative in meaning more human trafficking, problems with body images and expectations about sex, and dehumanization of women.
An increase in demand is usually environmentally destructive. An increase in demand is also usually morally destructive, meaning more crass materialism and greed.