The Chesterton's Fence argument is about knowing the purpose of something and being able to understand the consequences of changing it. With older traditions both are harder.

This is turning the argument on its head.

The point isn't that knowing a purpose for something is a reason to keep the thing. If we know the reason for it and judge it good, of course we shall keep it. Banal. If we know a reason for a thing, and judge it bad, then the argument isn't an encouragement to keep it either. No Chesterton's Fence is the argument that us not knowing the reason behind something is a reason to keep it. Applying it to things, for which we easily learn why they are there, is pretty much redundant as far as heuristics go.

Let me quite directly, from his novel The Thing (1929). In the chapter entitled, “The Drift from Domesticity” he writes:

In the matter of reforming things, as distinct from deforming them, there is one plain and simple principle; a principle which will probably be called a paradox. There exists in such a case a certain institution or law; let us say, for the sake of simplicity, a fence or gate erected across a road. The more modern type of reformer goes gaily up to it and says, “I don’t see the use of this; let us clear it away.” To which the more intelligent type of reformer will do well to answer: “If you don’t see the use of it, I certainly won’t let you clear it away. Go away and think. Then, when you can come back and tell me that you do see the use of it, I may allow you to destroy it."