>You could better refute this by starting with a policy you would consider cruel, and the in turn demonstrating how this one doesn't fit it.

I actually don't think it is that common for policy to be cruel just for the sake of being cruel ("the cruelty is the point")

>For a while they were deporting people to the equivalent of a Gulag, and literally suggested that if people were afraid of that outcome they should self deport. I think that would be a pretty fair example of a policy where the cruelty was the literal point: The hope was it would be viewed with sufficient fear as to dissuade people from staying in the country illegally.

The point of law enforcement is to deter and prevent lawbreaking, not be cruel for its own sake. Suppose you observe that meals in prison aren't very tasty. Would you criticize this policy on the grounds that "the cruelty is the point"?

You can argue that the punishment is too harsh, but that still doesn't prove that cruelty was the point.