The other issue is that it tends to be underspecified whether a discussion is about law or policy.
Someone comes in and describes from first principles what a reasonable system would look like, and then someone else haughtily chastises them because that isn't how the existing system works. But if you read it as they intended it, i.e. as a policy proposal rather than a legal opinion, then the fact that it isn't the existing system is the point. The intention is to change the system to make it that way and the desired response is either support or a criticism of the mechanics of the proposal rather than its basis in existing law.
On the other hand, many people who reason from first principles fall into two fallacies:
First, they believe that their system is how the world should work, and therefore how it would work if only someone, somewhere, weren't interfering. The result is conspiracy theories.
Second, they have not fully thought out the consequences, or don't care about them, and dismiss the historical consequences of similar systems in the past. Reasoning with people who ignore evidence in favor of their theorizing is difficult.
Someone comes in and describes from first principles what a reasonable system would look like, and then someone else haughtily chastises them because that isn't how the existing system works. But if you read it as they intended it, i.e. as a policy proposal rather than a legal opinion, then the fact that it isn't the existing system is the point. The intention is to change the system to make it that way and the desired response is either support or a criticism of the mechanics of the proposal rather than its basis in existing law.