includeIt is written in More Dakka:
If something is a good idea, you need a reason to not try doing more of it.
Taken at face value, it implies the contrapositive:
If something is a bad idea, you need a reason to not try doing less of it.
This is not the contrapositive. It is not even the opposite.
Maybe these students are purposely misinterpreting “Native American” to be someone who was born and raised in the United States, perhaps with ancestors born and raised in the US as well. This is actually the older sense of the term “Native American”, found, for example, in the name of the Native American Party back in the mid-1800s.