Does "It clearly isn't" refer to "the Bible clearly isn't the best way"?

And "on the subject" refers to "on the subject of morality"?

Context:


In response, Christians like yourself often point out that the abolitionists also drew considerable inspiration from the Bible. Of course they did. People have been cherry-picking the Bible for millennia to justify their every impulse, moral and otherwise. This does not mean, however, that accepting the Bible to be the word of God is the best way to discover that abducting and enslaving millions of innocent men, women, and children is morally wrong. It clearly isn't, given what the Bible actually says on the subject. The fact that some abolitionists used parts of scripture to repudiate other parts does not indicate that the Bible is a good guide to morality. Nor does it suggest that human beings should need to consult a book in order to resolve moral questions of this sort. The moment a person recognizes that slaves are human beings like himself, enjoying the same capacity for suffering and happiness, he will understand that it is patently evil to own them and treat them like farm equipment. It is remarkably easy for a person to arrive at this epiphany - and yet, it had to be spread at the point of a bayonet throughout the Confederate South, among the most pious Christians this country has ever known.