Examples:

1. There must be life elsewhere in the universe, otherwise the universe would be a lonely and unappealing place.
2. Science must be able to explain everything we see. If it can't we could never really be sure of anything.

The New England Skeptical Society wrote up a great document about the Top 20 Logical Fallacies at http://www.theskepticsguide.org/resources/logicalfallacies.aspx. For Agrument from Final Consequences, they wrote:

Such arguments (also called teleological) are based on a reversal of cause and effect, because they argue that something is caused by the ultimate effect that it has, or purpose that is serves. For example: God must exist, because otherwise life would have no meaning.

the world would be a better place if people everyone knew what this means so we should teach them

would be an example