It's really hard to read this comment as anything other than "don't worry about the genocidal policy of the US with regards to the natives, for they were a violent people."

Indeed, it's actually an example of problem I lamented: the disinterest in covering Native American history post-founding of the US. The last of major conflicts between different Native American tribes took place around the 1850s, the lingering effects of the Lakota being pushed onto the Plains [1]. From that point on, all of the main conflicts are between the US and the various Native American tribes for a variety of reasons, although mainly "the US wants your land and isn't going to take 'no' for an answer."

[1] If you want to analyze the broader historical context, you of course have to ask "why did the Lakota move onto the Plains?" and following that thread of logic leads you to the first cause being "the English settled on the eastern coast."