What principle follows from contrasting «هٰذا العالم الفاضل» and «هٰذا المفسد»?

Defining the Subject by Demonstration: Rhetorical Purposes of Demonstratives

• A demonstrative always produces a false claim
• One demonstrative can praise or disparage according to context
• Demonstratives are disallowed in eloquent speech
• Only the first sentence has a subject