In 1890 the Sioux were not US citizens, so 2A just did not apply to them.
They were citizens of a nation at war with the USA.
You can make a decent case that WK was a war crime, but you can’t make a case that it was a violation of the constitutional rights of the Sioux. They didn’t have any.
BTW, I do find it interesting that the America-haters constantly talk about the few cases, mostly Wounded Knee and Sand Creek, where US troops committed actrocities against Indians. But these were greatly the exception.
Nobody ever talks about the fact that most tribes as their normal routine of business did much worse every chance they got.
Obama saying we are right wing extremists/terrorists at war with this country is entirely an exercise in semantics. If the words appear on his teleprompter, he will say them.
Was Waco an “act of war”?