I think you were disturbed before my sentence, disturbed by the truth. There was NOT a "complete wiping out of the culture"; no more than there is a complete wiping out of American Indian culture.
Culture in ANY civilization is encroached upon by the discoverers (immigrants and - in the past: the world explorers). The home culture changes; ALL cultures change over time.
NO culture of any time in history has remained unscathed. No language remains unchanged, it changes with time and things like: the internet!
Have you studied cultural anthropology?
Cultures change. Change is inevitable. How the change occurs can be either violent or civil, or a combination of both and many surprise world events, and social evolution.
Rape and murder occur in most cultures/countries taken over and then colonized. This is because men have historically been the explorers, or people who come take over the country (space, resources, even WOMEN have been taken over if there is a lack of women back home...). Also women were not available at the time of the rapes, because men left their wives to take care of their family left behind.
Rape and war are bedfellows - especially in past history, as well as modern history; it is a terrorist methodology of inciting terror and fear; control.
The Europeans taking over and settling places such as AUS and US, the Americas, they saw indigenous peoples. Some friendly some not friendly. The indigenous peoples were tribal, and were often NOT friendly to each other - warring and raping and killing whichever tribe didn't suit their fancy. So the people that were settling aka colonizing at the time, thought it was GOOD (they thought what they were doing was best for the indigenous people: to indoctrinate the natives to their way of "civilized" culture. Some was probably borne of good intentions, some maybe not so good of intentions.
But is anyone justified in these modern times to punish, ask for apology, or for reparations of others of us modern time peoples, for those ignorant things all our ancestors did in the past??