Season 8
Plot:
Immigrants from the future travel to the present in search of jobs and better living conditions. The reason?: The future is a disaster product of overpopulation and the unsustainable behavior (in ecological and economic terms) of present-day humans. Gradually, the immigrants of the future begin to saturate the labor market, taking away jobs from present-day people thanks to their willingness to work for very little money. This obviously creates discontent and immigrants are discriminated. The affected citizens meet and conclude that the only (and "brilliant") solution to the problem is to prevent the future from happening. For this, they conclude, it is necessary for all people to become homosexuals: if no one reproduces there can be no future.
Analogy:
Quite obvious in this case: South Park represents the developed countries and the "future" represents developing or underdeveloped countries. The motivation for men in the future to travel back in time is the same reason why people in poor countries try to emigrate to rich countries. The reason why the future is a disaster is also the same reason why some countries are rich and others poor: the first ones (only because they "arrived first") exploit the resources of the second ones and keep all the benefits. Just as today we are selfish with future generations by exploiting natural resources and polluting without assessing whether this will allow our grandchildren to enjoy the same quality of life we have today.
Moral:
Sustainability should not be only understood in temporal terms but also in spatial or regional terms. The unfair extraction of resources from poor countries creates problems that are perceived in the short term. The most obvious one is the misery of the exploited countries, generating illegal immigration with all its negative externalities. The solution to the problem is obviously not stopping immigration, but the conditions that trigger it. Trying to stop immigration without understanding its causes is a policy as "brilliant" as preventing the future from happening.
We should not only try to make the future a place where humans will be able survive, but also the present. Today, you just need to go to a poor country to have a sort of vision of what the future would be if we don't behave in a sustainable manner. The poverty in underdeveloped countries is the spatial (and current) version of possible future disasters like global warming.
To have a brilliant future, we need to start by having an equitable present.
Disclaimer: Professor Chaos speaks Spanish originally (and refers to himself only in the third person). He apologizes for his awful (and probably chaotic) English. If you happen to speak spanish you might prefer to read the spanish version of this post
here