If the founders were strongly against interracial marriage (as they may have been- although remember that at least a few had children with their Black slaves) and wished to include that as a government-imposed policy it is "unfortunate" that they failed to explicitly include that in the Constitution. You are arguing that because some, maybe even many, people now guess that this must have been the founders' thinking at the time they drafted the Constitution that this guess should now be the basis of the current law. However, there are a lot of guesses/opinions on these types of issues. Gee, there should be some way of having a formal group of appointed legal scholars who are considered experts in the correct interpretation of the Constitution and who are expected to judge these issues as they arise. Oh wait, we have that: the judges on the Supreme Court. But you argue that they are wrong in their published interpretation of the Constitution. Why? Because you see it differently.