Ezra 9-10 and Nehemiah 13 relate occasions upon which the Jews were rebuked for contracting marriages with non-Israelite wives. Kinists argue that these passages demonstrate that the Bible condemns interracial marriage in general. But let's have a look at what the historic commentators upon these texts have to say about the issue:
"And Shecaniah the son of Jehiel, of the sons of Elam, addressed Ezra: “We have broken faith with our God and have married foreign women from the peoples of the land, but even now there is hope for Israel in spite of this"(Ezra 10:2).
"As soon as the people heard the law, they separated from Israel all those of foreign descent"(Neh. 13:3).
"Did not Solomon king of Israel sin on account of such women? Among the many nations there was no king like him, and he was beloved by his God, and God made him king over all Israel. Nevertheless, foreign women made even him to sin. 27 Shall we then listen to you and do all this great evil and act treacherously against our God by marrying foreign women?”"(Neh. 13:26-27)
"Thus I cleansed them from everything foreign, and I established the duties of the priests and Levites, each in his work"(Neh. 13:30).
Matthew Henry on Ezra 10:1-5:
10:1-5 Shechaniah owned the national guilt. The case is sad, but it is not desperate; the disease threatening, but not incurable. Now that the people begin to lament, a spirit of repentance seems to be poured out; now there is hope that God will forgive, and have mercy. The sin that rightly troubles us, shall not ruin us. In melancholy times we must observe what makes for us, as well as against us. And there may be good hopes through grace, even where there is the sense of great guilt before God. The case is plain; what has been done amiss, must be undone again as far as possible; nothing less than this is true repentance. Sin must be put away, with a resolution never to have any thing more to do with it. What has been unjustly got, must be restored. Arise, be of good courage. Weeping, in this case, is good, but reforming is better. As to being unequally yoked with unbelievers, such marriages, it is certain, are sinful, and ought not to be made; but now they are not null, as they were before the gospel did away the separation between Jews and Gentiles.
Albert Barnes on Ezra 10:2
"Jehiel was one of those who had taken an idolatrous wife Ezra 10:26; and Shechaniah had therefore had the evil brought home to him."
Keil and Delitzsch on Ezra 10:2:
Namely, the commandments "which Thou hast commanded by Thy servants the prophets, saying, The land unto which ye go to possess it is an unclean land through the uncleanness of the people of the lands, through their abominations, wherewith they have filled it from one end to another through their impurity. And now give not your daughters unto their sons, neither take their daughters unto your sons (for wives), nor seek their peace nor their wealth for ever; that ye may be strong, and eat the good of the land, and leave it for an inheritance to your children for ever." The words of the prophets introduced by לאמר are found in these terms neither in the prophetical books nor the Pentateuch. They are not, therefore, to be regarded as a verbal quotation, but only as a declaration that the prohibition of intermarriage with the heathen had been inculcated by the prophets. The introduction of this prohibition by the words: the land unto which ye go to possess it, refers to the Mosaic age, and in using it Ezra had chiefly in view Deuteronomy 7:1-3. He interweaves, however, with this passage other sayings from the Pentateuch, e.g., Deuteronomy 23:7, and from the prophetic writings, without designing to make a verbal quotation. He says quite generally, by His servants the prophets, as the author of the books of Kings does in similar cases, e.g., 2 Kings 17:23; 2 Kings 21:10; 2 Kings 24:2, where the leading idea is, not to give the saying of some one prophet, but to represent the truth in question as one frequently reiterated. The sayings of Moses in Deuteronomy also bear a prophetical character; for in this book he, after the manner of the prophets, seeks to make the people lay to heart the duty of obeying the law. It is true that we do not meet in the other books of Scripture a special prohibition of marriages with Canaanites, though in the prophetical remarks, Judges 3:6, such marriages are reproved as occasions of seducing the Israelites to idolatry, and in the prophetic descriptions of the whoredoms of Israel with Baalim, and the general animadversions upon apostasy from the Lord, the transgression of this prohibition is implicitly included; thus justifying the general expression, that God had forbidden the Israelites to contract such marriages, by His servants the prophets. Besides, we must here take into consideration the threatening of the prophets, that the Lord would thrust Israel out of the land for their sins, among which intermarriage with the Canaanites was by no means the least. Ezra, moreover, makes use of the general expression, "by the prophets," because he desired to say that God had not merely forbidden these marriages one or twice in the law, but had also repeatedly inculcated this prohibition by the prophets. The law was preached by the prophets when they reiterated what was the will of God as revealed in the law of Moses. In this respect Ezra might well designate the prohibition of the law as the saying of the prophets, and cite it as pronounced according to the circumstances of the Mosaic period.
The problem with the marriages contracted by the Israelites is that they were set apart as God's peculiar people, to whom He had given the Law. This made them unique possessors of the true religion among all the peoples of the earth (Deut. 7), and on account of this, they were not to marry with other races and thus risk adulterating the pure religion with the idolatrous practices of the other nations. The problem is purely religious, not racial.