Manhood, as Raspberry cogently notes, is learned in different ways and places, with different outcomes, depending on a growing boy's environment. Manhood can mean anything from gentle, quiet strength to brutal macho , and I think he is absolutely right to focus on the "dearth of positive male role models" as the source of problems in the development of manhood.
Now, here's the rub: there is almost no social/psychological research that investigates whether there is actually a developmental need for same-gender role models, and what the effect might be of having or not having such adults in a child's life. It is as if everyone just assumes 1) that children need same-gender adults as they grow up and 2) that the family will provide them.
Let me urge any and every agency that cares, public and private, to begin supporting such research immediately, and see that it filters into social policy as soon as possible.
Affiliated Institute for the Study of Women and Men in Society, USC