I have no problem with the principle of a fine for this, but it should firstly take into account the severity of the infringement and secondly the financial status of the person (i.e. if you're very wealthy R150k is not huge, but if you're an unemployed homeless pensioner it seems out of proportion).
But most importantly, it must be fair, and the same principle applied to all racists. For example, Velaphi Khumalo called for whites to be hacked and killed like Jews and skinned alive. This IMHO goes far further than Sparrow's unsavoury racial slur, yet where is his fine? There have, in fact, been numerous well publicised anti-white racist or hate speech comments on FB in recent months and not a single one of them has resulted in a fine, which makes the whole principle of punishing hate speech a farce. If it is not applied fairly across the board, it cannot be taken seriously.
The scary part is that where white racism tends to be racial slurs and insults, the other side is far more militant and directly calls for terrible violent actions against whites - but do you hear any outrage, any fines being imposed, anybody bothering to track down the owners of those FB accounts? Nope, crickets.