...whenever the law expands the freedoms of one person or group, it necessarily contracts those of another.
This is the "your demand to be treated as a human being interferes with my freedom to discriminate against you" argument. Is that what passes for legal thought at St. Thomas? The whole line of reasoning is blatantly self-serving on its face, and isn't any more morally sound when dressed up as an issue of constitutional law.
I have been reading some economics lately ("The Undercover Economist"--- not recommended unless you're looking for a basic primer, and even then I think you can do better.) So I was primed to cast this in terms of Pareto efficiency. Dr. Delahunty's argument is basically that all legal regimes are in a state of Pareto optimality--- it is not possible to make any person more free without making somebody else worse off.
Not only is this a depressing outlook, but it seems entirely at odds with any notion of institutional and societal progress at all! Are we to argue that constitutional government is no better than the divine right of kings, because the king's freedom to be a tyrant has been limited? Should Prohibition have been kept in force because "expanding freedom" to drink would reduce the freedom of mobsters to profit from bootlegging? (Or the freedom of bluenoses to impose their moral code upon others?) What "freedom" did anti-miscegenation laws protect? To be fair, Dr. Delahunty admits that we are allowed to make "trade-offs", but he is wrong to insist that all human interaction must be viewed in this light.
Further, orthodox Christian doctrine tells us that the freedom to sin (or to oppress, or to hate, or to "swing one's fist") is not freedom--- it is slavery. We cannot make ourselves more free at the expense of others. We become free only by grace; and the response to that grace is love, not insistence on one's "rights."
I don't know how to write the humanist version of the previous paragraph, but I'm pretty sure there is one. The notion of A's "freedom" to control B is either complete nonsense, or the worst sort of "might makes right" thinking. It's incompatible with either Christian values or Enlightenment ones.