For moral consensus to be a reality in this country there must be a foundation. I’ve argued that this foundation could perhaps be the constitution or similar documents, even as I’ve admitted that this would mean that homosexual and heterosexuals would be viewed equally before the Law. But how does this fit with obvious Biblical morality which declares homosexuality sinful?
There are two points that must be made before that question can be answered. One is that moral consensus in America is a political idea, not a Biblical one. There is no consensus in Biblical morality; God declares what is moral and honoring to Him, therefore it is. Second, Biblical morality for the Christian influences political moral consensus, not vice versa. Thus, one solution which has been offered on this blog is to eliminate financial benefits for both types of marriages rather than having benefits only for one or for both. But these two points often distract from the real issue at stake and the real answer to the above question: there is no political answer to true transformation.
Let’s assume for just a moment that the proverbial Presbyterian pastor and the homosexual man in the gas station late one night do indeed reach a moral consensus. Does this mean that true moral transformation has taken place? Absolutely not. Even if the pastor agrees that homosexuals and heterosexuals should be treated equally before the Law, it does not change the fact that he believes homosexuality to be wrong. Even if the homosexual agrees that the political promotion of homosexuality would be bad for the country, he will most likely remain homosexual, even if privately. Moral consensus would create, by definition, at atmosphere where both perspectives meet in a middle group, but this is also the limitation of moral consensus. In the depth of his soul, the Presbyterian pastor does not simply want equality but the transformation of the homosexual. The topic of moral consensus is a fun academic exercise, and would even create a wonderful atmosphere for American society, but the goal of transformation of individuals would not cease simply because consensus had been reached. Rather, moral consensus would create an atmosphere where the goal of transformation of individuals could take place even easier!
The danger of political discussion among Christians is that it is often seen as the goal, which it is not, transformation is. Politics is often seen as the means, which it is not, the gospel is. Thus, while moral consensus would be great, it cannot be the final objective. For true cultural and individual transformation to take place, true gospel impact must take place, creating a change that goes much deeper than moral consensus.
We could reach a moral consensus in the sense that we agree that it is moral to not criminalize all sin (to restate somewhat your conclusion in the third paragraph). This would be something like an Augustinian/Thomist prudential political philosophy:
“Although every crime is a sin, not every sin is a crime” (Augustine, Enchiridion).
“Human laws do not forbid all vices, from which the virtuous abstain, but only the more grievous vices, from which it is possible for the majority to abstain; and chiefly those that are to the hurt of others, without the prohibition of which human society could not be maintained: thus human law prohibits murder, theft and such like” (Aquinas, ST).
But from this it does not follow that the law is required to make no distinctions, or to treat unequal things equally.
To wit: Distinguishing Morality and Legality: The Practical Fusionist Possibilities of Thomas Aquinas http://www.cato-unbound.org/2013/05/30/jordan-ballor/distinguishing-morality-legality-practical-fusionist-possibilities-thomas