My bet is that this was just a stupid lapse of judgement, for which Mr Botha will pay dearly. I don't necessarily believe that this email betrays any particularly virulent strain of racism. Instead I believe that it's just another case of some random Afrikaner half hankering for some past that never really was, who is socially surrounded by people just like him, so he doesn't get the corrective feedback that would have prevented this turn of events. Just look at that list of executive managers: 14 of those 15 are lily-white - which one of them is likely to reply to some random politically-incorrect joke he trots out on Monday morning, pointing out that it's really uncool? Where on the list of priorities do you think "Be my colleagues' PC nanny" appears?
Should his head roll? I'm not sure about that. I am sure that there should be some form of punishment; after all, he is a leader in a company - a symbol, if you like, of what that company values, and symbols have meaning. But should he be forced out? That's less clear to me. I think Dr Hadebe is right to confront Mr Botha, and Aveng, but I think he overanalyzes the content of the email. IMHO it's just a stupid email sent in a stupid moment by a man who should know better.
I would like to see a more nuanced discourse on racism in the South African political economy. I'd like to see a distinction between this sort of overt offensiveness (that I hesitate to call "racism" - when my white friends tell these sort of "jokes" they seem to me more like toilet humour than a genuine expression of their beliefs), and the covert racism that you can really only notice if you're at the receiving end, or if you reduce it all to numbers, or pay closer attention to your surroundings than what narrow self-interest demands. Like when all the white staff at one of our offices has keys to the office, but "there are no spare keys left" when a non-white colleague joins. Or when my first instinct is to believe a white guy who asks me for gas money, but to expect the lone black executive among the 15 to be an "affirmative action appointment". Having a mini media storm every few years about some stupid emailed joke distracts us from the real issue.