Whether they "deserve" it or not is a never ending conversation because it is one based on morality and philosophy, two very subjective aspects of discussion.
Does someone inherit his father's sins? Tricky question. We could brush it off by saying father and son are two different entities but even science doesn't fully concurr as they share important quantities of the same genes. A son is literally half a copy of his father genetic-wise.
Does it justify considering their experience as the same? When a father's legacy goes to his son we do not question it as he bears the name of that man and that makes it his heir. Why would it be different with negative aspects of inheritance?
I believe we would think that global morality would see it as cruel because we tend to think everybody deserves a chance at life, and collecting our ancestors' burden could make it impossible to suffer.
I'd advise we look at how the father's deeds affect the life of his son. If the father's sin continues to live on through the son's life, I think the call can be made that it has to be corrected by the son himself or anybody that can. If the father's sin died with him, then there is nothing to be passed on.
In this particular case, the problem is that the sin of the Boers is still present to this day and is even maintained by the actual Boers and their descendants. Nothing, since Mandela came in power, has been made by these farmers to make the situation more equal, no step has been taken to share the disproportionate amounts of lands they possess with the rest of the country. And when action is taken to fix the situation, it is met with agression from those who profit the most of the situation.
In my personal book that make them all the more deserving of what's happening.
At the end of the day, it doesn't matter what people deserve or not. What matters is what's happening.
And it seems to be happening