Arguments about stolen land are hollow. Even those "natives" migrated from elsewhere. Many of the "native" tribes were also savage and brutal and warred against one another while some befriended the Christian settlers, allying with them against other tribes. A much more complex history than "we stole their land".

Also, slavery was a historical norm until Christians put an end to it. If you are going to start making arguments about slavery you need to ask why it is no longer legally practiced. That is the historic abnormality, not the presence of slavery or the morally complicated actions of our forefathers.

The points you bring up are worthy of discussion but none of them invalidate the moral, just, reasonable, and dutiful desire to defend ones country and culture from a foreign people's who care nothing for either. This is natural for any nation who wishes not to commit national suicide.