It is a fact that deer are shot in large numbers all over Britain; with little or no predation the deer population is only limited by food and culling is a normal (some would say essential) part of deer management in the UK today.

This is usually carried out in a very low key way by stalkers who have an interest in improving the herd; they will intimately know their herd and will select specific animals (those who advancing age leave vulnerable to starvation etc) to remove to maintain viable numbers and the balance of deer in the area
In such culls the stalkers are legally required to use firearms and ammunition of an appropriate calibre for the species

It seems that the Emperor was a dominant stag still in his prime, not yet on any list for culling due to old age and, although it may be possible to construct an argument that his dominant position was ultimately not good for the gene pool of the herd, it seems that his slaughter was purely as a 'trophy' animal

The UK system of land ownership and game laws means that landowners have free rein to kill permitted species on their own land – or sell those right to others!

Sensible 'management' is not the same as commercial greed