Sorry, let me ask a different way, how do the law makers justify this distinction? Presumably they aren't outwardly racist. So how do they justify harsher sentences to one type over the other type?

The law makers occasionally are outwardly racist, when they are unaware that the cameras are on.

The justification is usually made with respect to "urban environments", "public housing", and "poor people", eliding over the racial implications.

Also, street gangs like the Crips, Bloods, and Vice Lords were turning streets into war zones as they struggled to gain control over the crack trade. Nowadays, black gangs control the PCP market, and sentences for that are harsher than something like Ketamine, another dissociative anaesthetic. The media are also all too happy to put a naked psycho running around, punching passing cars, on their evening news.

The legislators can try to justify it all they like, but all of us watching can clearly see that whether it is intentional or not, causative or merely correlative, the mandatory sentencing laws are putting more black people into prison, and keeping them there longer. "Three strikes" laws are having a similar effect.

Frontline has a good writeup about it: http://www.pbs.org/wgbh/pages/frontline/shows/snitch/primer/

There was public hysteria over crack, and Congressional Democrats wanted to show they were "tough on crime."

The article doesn't take into consideration at all the dramatic negative effects that the introduction of crack cocaine into black communities had. It's very easy to say that legislators irresponsibly put back mandatory minimums after they were carefully considered and removed in the 1970's, if you don't see the crack epidemic of the 1980's as the hugely significant event that it was. I don't think it was hysteria, it was a huge problem.

Huge problem or not, the Congressional response was—in retrospect—an unmitigated disaster. The actions recently taken to reduce the disparity between crack and coke sentencing guidelines helps, but does not solve the problem.

You're laboring under the assumption that these laws are to protect people from hurting themselves.

This should help disabuse you of such thinking. The Racist War on Drugs: https://www.youtube.com/watch?v=wONAqaxgIoo

Who says they justified the distinction?