“...And the flag represents the nation as it was founded, the constitution, which does not endorse slavery...”
Article I, Section 2, of the U.S. Constitution of 1787 in fact declared that for purposes of representation in Congress, enslaved blacks in a state would be counted as three-fifths of the number of white inhabitants of that state.
Clearly it has been corrected.
“The Thirteenth Amendment (Amendment XIII) to the United States Constitution abolished slavery and involuntary servitude...”
That’s the Constitution. The flag represents this, not the original.