Rather absurd. Two questions for the geniuses who dreamed up this policy:
1) With all the antidiscrimination laws on the books, aren't they worried about a lawsuit from a male pax who gets bumped because of their policy? Mind you, with the legal climate nowadays just about any business decision is a case of doomed if you do, doomed if you don't.
2) If they're really concerned about the kids' safety perhaps they shouldn't allow family members to travel with them- in the overwhelming majority of cases where kids are victims of crime the guilty party is their own mother.