Here’s one line of thought: some things make humans happy or unhappy naturally. The best societies are those with the happiest people. Therefore, governments should aim to make the people as happy as possible: a task that requires expertise on conditions conducive to happiness. Social scientists provide that expertise. They can also help sell political agendas.
Take the case of “inequality-aversion” – the idea that humans don’t like inequality. According to this theory, inequality aversion is in our DNA, an adaptation from harsher times when sharing was essential to survival. It is therefore natural to be distressed about inequality and to feel better when resources are more equally distributed. Thus, the best societies are more equal, because more equal societies are happier societies.
If things were only that simple. One problem is that on the macro-level, country-wide correlations between inequality and happiness say nothing about causation. And on the micro-level, people vary in their reactions to inequality, depending on how they see its causes and effects. For instance, if one believes that long term poverty is the result of bad choices, the fact that some people are worse off than others may not be all that upsetting. But if one believes that affluence is mostly a matter of luck, inequality may very well trigger outrage. Point is, no one has an emotional reaction to inequality without a sense of what it speaks to. Inequality is a concept, for God's sake. It's not at the same level of concreteness as, say, a snake slithering in the grass.
Social scientists are people too, with their own intuitions about human nature, happiness, inequality and ideal societies. I'm talking economists, psychologists, sociologists, anthropologists (etc). I'm talking about the people who made up the theory of inequality-aversion.
The research social scientists conduct and the conclusions they reach are not independent of their intuitions about what is and ought to be. That's no reason to dismiss their work, only a plea to be alert to possible lapses of scientific rigor in what they do and say.
Next: How Democrats, Republicans, and Trump-Supporters look at Inequality