To address the instance first - I think use of the phrase does not show malice or racism, but it does show carelessness and lack of judgement, and those are things that no-one in public life can afford to exhibit - so a sanction is appropraite to show that the government is aware of such issues, and does not allow them to pass unoticed.
As to Naomi's well-reasoned argument that the sting can be taken out of any offensive term if the objects of it are willing to act as one - that is unfortunately arguing on the basis of logic, which does not allow for human nature.
Black people are stigmatised - not to anything like the degree they have been in the past - but a degree of stigma is still present, and black people are sensitive to it.
In terms of black people using the word '***' amongst themselves, that is simply the ownership of an insult taken back by its recipients, and losing its venom in the process.
As a white middle-class man, I could argue that this is pointless posturing, which incidentally I don't, but I have no direct experience of racism, and how it feels, maybe if I did, I would view the issue differently.
I think it is easy to scoff at the ways different people deal with their social issues - if you don't suffer from the yourself, and part of being a sensible balanced human being is awareness of the senstivities of others. That doesn;t mean agreeing with them, or championng them, but a little tolerence is free, and helps the world to turn that bit more smoothly.