Ask Lemmygrad

Many indigenous societies practiced slave economies, regularly destroyed their own environment, waged brutal wars, massacred civilians, tortured captives, ritually sacrificed people, raped women, kidnapped children, performed cannibalism, and yes some even scalped people (though this one wasn't a native development but rather poetic revenge for colonists scalping them first) and other terrible things because they weren't oh-so-noble and honorable people who were somehow more moral than the colonizers. That perception of indigenous people is as much a racist stereotype as the ones that try to conflate all the above things with every tribe, city-state, nation, etc. and act like they were uniquely evil for doing these things and needed Good Christian Values™ to "civilize" them.

It is possible to recognize that these societies weren't perfect and to not romanticize them while also opposing their aggressive destruction at the hands of white supremacists, who either exaggerated their worst attributes or in some cases just made shit up to justify ethnic cleansing, segregation, and land theft. Whenever someone says something like "Native Americans owned slaves" it is not being brought up as a statement of fact or a tidbit of history but for the purpose of driving a wedge between indigenous and black people; just as when people bring up the Buffalo Soldiers and other black units that helped terrorize indigenous communities. They aren't mentioned these things in good faith, they're being racist and trying to turn marginalized communities against each other to keep them divided. Reactionaries do this because they fear a united front. This is an example of how identity politics get weaponized against the Left.