Robinson doesn't rely on anecdotal evidence. Anecdotal evidence would involve citing a specific example to support a broad conclusion. Robinson's premises are general claims about the condition of the items and how they can be made available, not claims about specific props or costumes.

Robinson's response fails to engage with the substance of Wexell's argument. Wexell's point is that the items lack artistic significance outside a performance. Robinson never disputes this. Instead, Robinson argues that displaying the items is the only way to make them available to the public, as though public availability alone justifies the purchase. By pivoting to a different reason for the purchase without addressing Wexell's core objection, Robinson leaves the heart of Wexell's argument untouched.

Robinson never criticizes Wexell's character, background, or motives. Robinson's response focuses on why the purchase was justified, not on anything about Wexell as a person.

For this to be accurate, Robinson would have to argue that Wexell's reason for thinking the purchase was wasteful isn't sufficient to prove that claim. But Robinson doesn't do that. Robinson never says anything like, "Just because the items lack artistic significance outside a performance doesn't mean the purchase was a waste." Instead, Robinson ignores Wexell's reason entirely and offers a completely separate justification for the purchase (public access).

You might be drawn to this answer because Robinson does state that displaying the items is necessary in order to make them available to the public. But Robinson doesn't confuse this necessary condition for a sufficient condition. A sufficient/necessary confusion would look something like: "The items can be made available to the public only if they are displayed. The items are being displayed. Therefore, they are available to the public." That's not what Robinson does. Robinson's flaw is that the entire argument sidesteps Wexell's point about artistic significance.