Right: Does it do good? Left: Does it feel good?
This seems about right, at least as far as pithy explanations go. It's certainly true that the left tends more towards subjectivism about value.
These fundamental stances explain the outrage and cries of racism directed towards Justice Scalia for noting a fact--that a lot of blacks flunked out of school due to affirmative action policies--and that they might be better off going to a lower tier school and passing. (Of course, as Scalia himself noted, this question only applies to those blacks (etc.) admitted with lower qualifications.) In short, he asked whether those policies actually do good. Simply asking that question is impermissible. Why? Those questions might make some people feel bad. This is essentially the objection that a panel on NPR reached the other day.