My point is mainly that the two "offences" (if we are to class racism as an offence), are vastly different, and in entirely differently classes.
To rehabilitate someone who made a joke in bad taste should be far, far easier than to rehabilitate a murderer. The two just cannot be equivocated. One is a criminal act, the other is expressing an opinion, albeit a very bad one.
Obviously, they are different, and the length of sentences reflect that. A murderer is in prison for 10-20 years and a really bad racist joke makes you unemployable for a year or 2.
There's also a problem with the verb "to rehabilitate" because much of the rehabilitation comes from the subject themselves and can't be imposed by society. The murderer who serves time, shows remorse, and studies programming to reintegrate society is different from the racist who doesn't apologize sincerely or believably for the bad joke and complains that nobody will hire them.
Finally, look at the environment that the rehabilitated person gets put into. Someone who got into drugs and gangs as a teen, went to prison, and then turned their life around is not a threat in an office environment. A racist or sexist may still cause disruption in a diverse and gender-equal work environment. The ex-gang member can't go back to the 'hood, but the racist or sexist has made it much more difficult to work in any office--or with people so that's pretty much any job. Though like I said, if they apologize and repent, I think the racist should be given a second chance as well.
To rehabilitate someone who made a joke in bad taste should be far, far easier than to rehabilitate a murderer. The two just cannot be equivocated. One is a criminal act, the other is expressing an opinion, albeit a very bad one.