Why has the issue of frontier violence provoked such intense debate? What is at stake here?

‘Terra Nullius’ – Land belonging to no one.
When the British arrived in Australia, they declared the land to be ownerless. Devoid of ‘human’ habitation.
Later historical narratives, though certainly acknowledging the presence of an Aboriginal population, still depict the colonisation of Australia by the British as ‘a peaceful act of discovery and settlement, whereby a progressive people and their venerable institutions were successfully transplanted and the land was transformed, thus resulting in the new nation of Australia.’ (p172) – Bain Attwood and S.G. Foster, Frontier Conflict: The Australian experience.
This version of history maintains that the Aboriginal population was small, and that the settlers were not taking land from them, because the Indigenous population supposedly were not using it.  As white settlers saw no sign of British agriculture or land management, they considered the land unused, and ripe for settlement and cultivation.
In the beginning, the British were attempting to understand a vast continent, populated by Aboriginal people with a culture and practices very different from their own. They drew conclusions from first impressions of people and places. The following is from Captain James Cook describes his impression of New Holland, August 1770.
‘I do not look upon them to be a Warlike People, on the contrary I think them a timorous and inoffensive race… neither are they very numerous’. (pp3-4)
This view of settlement - that the Aborigines were not numerous, and that settlement through hard work made use of uninhabited land - continued to pervade our notions of history, and became part of the Anglo-Australian sense of national identity.

Frontier Violence has always had a place in recorded history, as revealed by this painting from 1861, depicting a battle at Bulloo. However the extent of the violence, and the reasons why violence erupted between Aborigines and Europeans, are still sensitive subjects which provoke intense debate.

Bulla, Queensland, 1861 – William Oswald Hodgkinson, 1835-1900.
Source -http://nla.gov.au/nla.pic-vn4189024-s46

 The issue of frontier violence however, posed a real challenge to a long accepted narrative of history.
As Bain Attwood and S.G. Foster argued - It has ‘provoked a crisis of confidence or conscience for many Australians,’ (p172) because the existence of ‘frontier violence’ suggests not that the land was unused and underpopulated, but that in many instances, Aborigines actively sought to defend their land.
Attwood and Foster also note:
'As a result, the following picture of the frontier emerged during the 1970s: Aborigines and Europeans used the land in quite incompatible ways as pastoralists’ cattle and sheep ate, trampled and fouled Aborigines’ sources of food and water; Aborigines were forced to steal the newcomers’ stock and other  property in order to survive and often launched attacks on the colonists; pastoralists and their men wreaked violence on Aborigines, killing large numbers in the course of conflict across the country.' (pp170-171)
‘Consequently, the settlement of this country has been rendered as an act of invasion, a process of conquest that dispossessed the rightful owners of the land and resulted in violence, racial discrimination and neglect which destroyed many Aboriginal communities and degraded most Aboriginal people.’ (p172)


References:

‘Captain James Cook describes his impression of New Holland, August 1770.’ in Deborah Gare and David Ritter (eds), Making Australian History: Perspectives on the Past since 1788, Thomson, South Melbourne, 2008, pp3-4.

‘Frontier Conflict: The Australian experience’ Bain Attwood and S.G. Foster, in Deborah Gare and David Ritter (eds), Making Australian History: Perspectives on the Past since 1788, Thomson, South Melbourne, 2008, pp169-174.