I don't think this is necessarily true. We just haven't seen many racist people make amends and ask for forgiveness. I believe people can change and if they do, they should be reintegrated into the workplace.
I hadn't given it much thought before, but I asked myself if I would hire or work with a former criminal qualified for the job. It's a touchy subject, but I decided I would if they are rehabilitated: shown remorse, served a sentence, and working to integrate society.
And I realized the same goes for a racist statement (or sexist or anti-LGBTQ). Racism get tried in the court of public opinion, and then there is a sentence of being shunned in the form of unemployability. But if the formerly racist person shows remorse and publicly states they have changed, I would be willing to hire/work with them.