Don't worry about being sued – those are just idle threats. The fact is that you can voice your opinions about others and their offerings freely according to the South African constitution last time I checked. So we want to hear what you think. 🙂
If he does decide to sue you, get the best and most expensive lawyer you can. He will almost certainly loose the case and then you sue him for your legal fees. He ends up paying. So if he has any savvy left he will get some manners back.