1. Morally good actions are those that increase the well-being of as many people as possible, either directly or indirectly (this approach to normative ethics is called utilitarianism.)
2. Accurate and useful information which is presented in compelling ways is likely to increase awareness of relevant matters. Good visualizations also enhance understanding and knowledge.
3. Good understanding of relevant matters can inform future decisions, so it is likely to increase the chances of people conducting fruitful, happy lives. In other words, understanding can have a positive influence on people's well-being.
4. Therefore, it is the obligation of the designer of visualizations to create graphics that (a) are intended to bring attention to relevant matters, (b) are based on a thorough analysis of the information, (c) are built in ways that enable comprehension. To do this, designers ought to base their decisions on scientific evidence or, in case that this is not available, on judgments derived from their experience and personal observations.
Read the IRE article below or download it here. By the way, its last line is a joke.