How would the remaining natives benefit from more immigration?
Even if your (stupid) premise is something like "turnabout is fair play," how is it even turnabout? How do people out on the rez benefit from more illegals OR legals?
How dare we learn from their experience?
The natives were already in sharp decline long before anyone touched their shores. Peace was offered and then shunned at every turn because native leaders thought it better to die standing than become subjugated. Be proud red man. You fought against something you had no chance of winning and stood fast to your ideals until facing down the very extinction of your people. That's better than most do.