Stay polite and don’t back down. Remind him that no developed nor undeveloped country at that time had multi-ethnic and co-ed forms of gov’t. Then remind him that those White Christians who he’s criticizing (use the term “White Christians”) laid the foundation for the very idea of a mulit-ethnic co-ed power sharing society to be possible.
Cheers!
Go thru the principal, to / with the teacher, and strongly recommend that he first survey other governments / societies of the time (including those represented by the local 'prior immigrants').
That should prove that slavery and servitude were commonplace worldwide, that the natives were not yet tuned into a broader nation, and that (oh, by the way) African slaves were not commonplace until after 1791.
After that lesson, suggest that they address how our founding fathers allowed for change, not to core principles but to the application of liberties to those who were not specifically addressed in the original.
Then you might suggest that various machinations (casinos, affirmative action, "hate" crimes, etc.) have come to pass as a means to obtain serious, and destructive, payback for any inadvertent oversights.
That is so true, and so unPC, but I repeat myself.
“White Christian Males” built this country and the concepts of individual liberty in Western Culture.