Ought we to compare principled opposition to gay marriage to the racism of our ancestors? According to Ashley Bean Thornton (“One day we will be ashamed,” July 6), the answer is yes. She wrote: “I believe a generation from now we straight people will feel just as ashamed at having tried to deny gay people the right to marry as we white people feel now at having tried to deny black people the right to vote and to be treated equally and fairly.”

Thornton’s essay calls for a calm, measured response and that is all I hope to offer here. First, however, I want to reaffirm what I have said on these opinion pages and elsewhere in the past. I am not opposed to civil unions between gay people with all the rights and responsibilities marriage traditionally carries. As a conservative Christian I am dubious about calling these unions “marriages,” but people can call them whatever they want to.

I worry, however, that Thornton’s essay will be misconstrued by some readers as an argument. It isn’t one. It is an opinion based on a perception of a comparison between racism and reluctance by some people to recognize gay unions as true marriages. That comparison and Thornton’s hypothesis about what “the next generation” will think of “us” fall far short of an argument. Thornton’s whole essay is, in my opinion, mere rhetoric, but I fear some will confuse it with an argument.

With all due respect to Thornton, I will dare to say that her essay is, whether she knows it or not, an attempt to create sensations of fear and shame. That is rhetoric rather than argument. We all need to learn to distinguish between a good argument, or any argument, and rhetoric. Rhetoric aims to convince through evoking emotions; argument aims to convince through evidence and logic.

Having said that, I admit that there is an implicit argument hidden in Thornton’s mostly rhetorical essay. It is, of course, that people who think gays should not marry are guilty of the same kind of ignorance and prejudice that drove people in the past (and, of course, some still today) to deny African Americans their full rights as human beings and as American citizens.

This implicit argument, however, in my opinion, ignores a reality and makes a false assumption.

Thornton seems to assume that the biblical case supporting racial prejudice is on the same level, exegetically and hermeneutically (both referring to the sciences of Bible interpretation), as the biblical case supporting belief that marriage should always only be between members of the opposite sex. This reveals ignorance of a fact and a false assumption.

The fact is that the imagined biblical case supporting racial prejudice and oppression of black people was always only that — imaginary. The Bible nowhere actually does support such. Racial prejudice and oppression were read into the Bible, not out of it. On the other hand, many serious biblical scholars such as Richard Hays of Duke Divinity School believe the Bible actually does exclude sex between persons of the same sex (as not God’s intention and as sinful). These two interpretations of the Bible are not really comparable. One is absolutely groundless and the other is not based solely on ignorance and prejudice.

A false assumption I believe I detect in Thornton’s essay is that just because our ancestors misinterpreted the Bible about racism we must worry that our contemporary interpretations of the Bible are false. I meet people all the time who assume and assert that just because “good people” interpreted the Bible wrongly in the past we must consider contemporary interpretations of the Bible dubious at best.

Finally, to repeat, creating fear that people who hold a certain belief might turn out to be “on the wrong side of history” (as some express the rhetorical “case”) should not be confused with an argument. It isn’t one. It is sheer rhetoric appealing to fear and shame.

Nothing I have said here should be taken as an argument against gay marriage; it isn’t. My only concern is to point out certain weaknesses in Thornton’s case insofar as she or readers mistake it for an argument.

Roger E. Olson is Foy Valentine Professor of Christian Theology and Ethics at George W. Truett Theological Seminary at Baylor University. His recent books include “The Story of Christian Theology: Twenty Centuries of Tradition and Reform” and “Who Needs Theology?” with Stanley J. Grenz. He is a past president of the American Theological Society (Midwest Division). He and Thornton are members of the Trib Board of Contributors.