St. Augustine asserts that there is a category of actions that are "lawful" but not "beneficial". He states that things that are allowed (not forbidden by any commandment of God) should be dealt with in the way that does most good.

Therefore, a mixed-race marriage falls under the category of "permitted by justice" (since no divine law explicitly forbids it), but it is classified as not good as it introduces harm in the temporal or generative sphere.

If a mono-racial union transmits a specific set of positive accidents, then a mixed union results in a negation or privation of those specific accidents. The offspring is deprived of the full expression of the accidents of either lineage.

Evil is classically defined as a "privation of good"(as evil itself does not exist but is a privation of goodness) or a negation of being where it ought to be, the loss of these specific accidental traits constitutes a "bad" or "evil" in the temporal sense.

And as we saw St Augustine state, We must avoid lawful things if they cause harm. Just because an act isn't a sin doesn't mean it should be done.

Here St. Augustine notes why in regards to natural reasoning it is better to not divorce an unbelieving spouse (which would be lawful to do) as it would bring about more evil. The same can be applied with mixed-race marriages as stated above in that they bring negatives.

Thus, one refrains from it not out of fear of divine justice, but out of a desire for the greater good of preserving positive accidents. It is not even the physiognomy itself that matters in this regard racially, But the psychological traits which matter the most.

So to sum it up, Through St. Augustine's logic, Since mixed-race marriage is not forbidden by justice, it is "permitted." However, because it results in a negation of accidents (a privation of the specific positive traits of a single lineage), it is not good.

Thus it would be rightful for the State to prohibit such marriages through the so called "negative eugenics" and to ensure the breeding of individuals is by positive psychological traits.

Historically too both the late Roman Christian Empire and Visigothic Kingdom had laws prohibiting marriage on ethnic grounds:

And we know it would be a cope to give a charge against "Negative Eugenics" being anti-Christian, As the Bulgarian Orthodox Church itself accepted them:

It is inherent that it is the job of the State to put some measures of marriage as recognized here by the Bulgarian Orthodox Church. The Church is an ecclesiastical institution and it's role is the spiritual while the State is supposed to guard and serve the natural.

So when the Church approves of a marriage(Which is contingent on State authority and Citizenship) It just approves of the Nation’s judgement on marriage and not the mixed marriages themselves. It isn’t approving of the mixed marriage itself but the marital contract constituted

The Church itself recognised that the State is the force that determines the legality of marriages and that it can even desolve them:

We see this as standing true to today.

St. Basil the Great states that marriages entered into without the consent of those in authority are fornications

The Church’s ban on first cousin marriages itself comes from natural law as such prohibitions are absent from Levitical laws and were not in place

And such a charge of "Calumny" against those criticising married Christians for having a mixed-race marriage cannot hold, As St. Bede does the same thing obviously in an eugenic sense by reading the whole text in context.

As we stated above, The Church isn’t approving of the mixed marriage itself but the marital contract constituted by the nation (Keep in mind there was no formal blessing for Matrimony prior to Byzantine law instituting it.)