OK, so one foot in front of the other. Change the debate. Present irrational and disproportionate "tough on crime" rhetoric with strong public opposition and make sure the demagogues fighting progress have to face the scorn and ridicule they deserve.

>There are certainly attempts (mostly at the state level) to downgrade victimless or harmless crimes, and to divert petty or juvenile criminals into non-penal programs or extrajudicial fora.

Which is well and good, though I think most of the problem lies at the federal level, so it would be nice to see more progress there.

>However, this is slow going; there are conflicting theories on the role of criminal law (consequentialist, deontological and so on) and no clear answer on the purpose of sanctions (deterrent, penal, and rehabilitative) that don't yield to simple analysis.

I think the key to this is to realize that the existing system doesn't adequately serve any of those goals. Consequentialists should be dissatisfied by the number of victimless crimes being prosecuted. Deontologically there are a great many "criminals" going unpunished because they violated the letter but not the spirit of the law, while those who violate the spirit but not the letter (or otherwise raise the ire of a prosecutor) are often prosecuted on the basis of "he seems like a bad guy, let's find something we can nail him with." Anyone interested in deterrence or rehabilitation can't be satisfied with the recidivism rate, and anyone interested in punishment (as distinguished from revenge) should be extremely concerned about the lack of proportionality.

Moreover, solutions that work in practice tend to satisfy everybody. Nobody who isn't being intentionally disingenuous is going to be dissatisfied by a reduction in the crime rate or the recidivism rate.

>Changing this will take a generation, or two.

Possibly. It depends how bad we want it and what we're willing to do about it.