I once wrote that "[l]iberty, to ... the 'libertarian' Left, is the 'right' to believe as they do." One "libertarian" Leftist is Will Wilkinson, who invites the wrath of Arnold Kling by invoking happiness research in support of his (Wilkinson's) evident bias against child-bearing. (See for example, this dissection of Wilkinson's position by Bryan Caplan.)
Wilkinson is so hard up for an argument against child-bearing that he ignores the libertarian doctrine of personal responsibility and falls back on "happiness research." Thus Kling's rightful wrath.