Beckwith's arguments were solid, and I particularly enjoyed his analysis of the oft-claimed need for political reasoning to be secular:
[Robert] Audi offers another principle that may be employed, the "secular reason requirement." It goes like this: one has a prima facie obligation not to advocate or support any law or public policy that restricts conduct unless one has and is willing to offer adequate secular reasons for advocacy or support.
...this principle requires, without argument, that the citizen's reason be secular. But "secular" is not a relevant property of a reason that is offered in support of a conclusion that an advocate is advancing. For instance, the terms "true, false, plausible, implausible" are adjectives that we apply to reasons to test the property relevant to its purpose as part of an argument. A property is characteristic had by something. So for example one can say "the dog is brown," which means the dog has the property of brownness. However, if one were to say "the set of all even numbers is brown," one would be saying nonsense. Numerical sense cannot have the property of color.
But reasons, like dogs or numerical sets, are things that can only have certain types of properties. Just as a dog cannot have the property of a rational number, and a numerical set cannot have the property of "blue," "valid," or "tall," a reason cannot be secular. For "secular," like "tall," "fast," "stinky," or "sexy," has no bearing on the quality of the reason one may offer in an argument to advance a particular public policy or point of view.
Suppose one believes the conclusion that unjust killing is morally wrong, and offers two reasons for it. The first reason is "the Bible prohibits unjust killing," and the second reason is "the philosopher Immanuel Kant's Categorical Imperative prohibits unjust killing." Most people would call the first a religious reason and the second a secular reason, because the first contains the name of a religious book, the Bible, and the second contains a non-religious principle, the Categorical Imperative. But how do the terms religious and secular add or subtract to our assessment of the quality of the reasoning?
If one, for example, has good reason to reject the authority of the Bible, then that good reason about the nature of the Bible is the good reason for rejecting that reason. On the other hand, if one has good reasons to believe the Bible is a better guide to moral philosophy than Kant's Categorical Imperative, in that case one ought to conclude that the first is a better reason than the second.
But again, how do the properties of "religious" and "secular" affect such a judgement? At the end of the day, reasons are weak, strong, true, or false, but "religious" and "secular" are not relevant properties when assessing the qualities of reasons a person may offer as part of her argument.
In practice, this requirement of secular reason functions as a hindrance for properly understanding the bioethical issues addressed and the positions held by Christian citizens.
To label an argument "religious" or "secular" is not to speak the language of logic but the language of anthropology or sociology. This tactic, widespread and often unconscious in use, tries to change the topic of the discussion from the argument itself to the category of person who is making the argument.
When this rhetorical shift takes place in jurisprudence, it suggests an implicit assumption that a certain type of people is in charge. Arguments are judged not on their merits but on whether they cater to this ruling type. The need to justify the rule of the secular tribe doubtless partially motivates the fervid insistence that the United States is a secular state.