Some would fight off soldiers to flee and sacrifice themselves so other Natives from their tribe could stay. The Seminole refused to leave and started a war called the Second Seminole War. Another war caused by refusual to leave was the Black Hawk War.
That could go both ways, maybe they didnt own a plantation or have use for a slave. But they still could support it. Or, they could be completely against it, and think its completely wrong and dehumanizing, they could help runaway slaves get to the north.
Answer: Directly for the best candidate
The leading argument against slavery during this time in the US was simply that it was immoral, and went against God's will. Another was that it violated the Constitution, and yet another was that it was unsustainable in the South.