A column in the latest issue of Metro (6/8/12, p.4) argues that people mistakenly think that forms of discrimination are illegal which are not, and tells people to get over their bias against discrimination, justifying this by reference to biased ideas about only children. I wrote this response:
Danny Cevallos's column is a good example of why we should maintain a presumptive bias against discrimination: the fact that it's so often based on a prejudice not supported by facts.
Cevallos justifies discrimination against only children on the basis of old stereotypes, without offering any evidence that they're true. Frank Sulloway's book Born to Rebel: Birth Order, Family Dynamics, and Creative Lives has shown that firstborns are more likely than laterborns to be eminent in traditional areas of achievement, but this is less true of only children. And even if only children were more likely to achieve, this would simply prove that their upbringing equipped them for achievement, thereby making them most suitable for eminence. Greater competence could hardly justify discrimination!
The only proper criterion for selecting people is individual merit. Any kind of discrimination, legal or not, is invidious because it's based on a prejudice about a group rather than the individual's qualifications.