Surely any violence is wrong. Doubly so in the face of a power impalance and intermingled family with livelihood.
Yes, of course it is. It doesn’t mean it doesn’t happen though, because people are human and in some circumstances, fuelled by fury or other strong emotions, they react in ways in which they would not choose to do if they were able to dispassionately consider the situation. Given that, if the violence used is not out of proportion to the situation, its generally regarded as regrettable rather than a permanent moral stain.
I’m not sure I see a power imbalance in a situation two fully grown male siblings, both with military training, having an argument? Worth pointing out here that Harry has also previously been in trouble for assaulting a photographer (he pushed his camera equipment forcefully into his face and cut his lip). And let’s not forget that the Princes’ mother was reported to have slapped her father and pushed her stepmother down a flight of stairs because she was so upset about the prospect of them marrying.