Ilya Somin makes some good points about how the War on Drugs affects black demographics:

As I have noted in the past (here and here), some 55% of US federal prison inmates and 21% of state inmates are non-violent drug offenders. And over 62% of incarcerated nonviolent drug offenders are black(most of them poor black males). I don't claim that this racial disparity in drug incarceration is caused solely - or even primarily - by racial prejudice. But even if undertaken for the best of motives, it drastically reduces the available pool of marriageable men in poor black communities. And, as Kerry notes, those men who remain have far less incentive to marry because their stronger bargaining position caused by scarcity makes it easier for them to obtain sex without making any longterm commitment to the women they do it with. Even after drug offenders are released from prison, they are likely to be worse marriage prospects than before, if only because it's hard to get a steady job after being in prison for several years.

Some conservatives might argue that the kinds of men who get arrested for drug possession or dealing wouldn't make good husbands even if they stay out of prison. Perhaps that is true in some cases. But these men still probably beat the alternative of single parenthood. Moreover, Kerry's point about bargaining position is crucial here. If fewer men from these communities were in prison, there would be more competition between them in the dating market and thus stronger incentives for them to behave in ways that appeal to women. To the extent that women prefer men who don't get high to those who do, that might well include staying off the drugs - as well as becoming better providers and fathers in other ways.

Ending the War on Drugs would certainly be no panacea with respect to the problems that the black community faces such as the rate of illegitimacy among black children. However, one need only look at the statistics cited above to realize that the War on Drugs has done tremendous damage to black demographics when it comes to the ability of black men to become stable providers and contributors to society. You cannot have such a large percentage of black men with black marks on their records for what are, objectively speaking, petty offenses without serious problems for black family life. Not only will it be harder for them to get good jobs, but it helps continue the poverty that fosters lower expectations about what sort of role black men can, should and must play in their communities.

To see evidence of what Somin says about black men having more power, one need only look at the disparity between college-educated black women and college-educated black men. There are significantly more of the former than the latter, and that gives college-educated black men a great advantage over black women. Not only is it easier for them to find a black woman at their social level than it is for a black woman to do the same, but their position also gives them more access to women of other races.

If drug dealing were no longer a profitable, black market enterprise, that would also provide incentive for more black men to do well in school and follow other social norms. The single biggest problem with the War on Drugs is that it gives many people a lucrative alternative to the normal economy for making a living, thus allowing them to effectively not contribute to society while making money.