Final answer:
Margaret's statement that 'all blonds are brilliant' is an invalid generalization, as intellectual ability cannot be determined by hair color. Additionally, dismissing her claim based on her natural hair color is a logical fallacy.
Step-by-step explanation:
The statement made by Margaret that "all blonds are brilliant" is a sweeping generalization and is therefore considered to be invalid. Judgments or assumptions about intellectual ability based on someone's hair color lack empirical evidence and are logically unsound, as brilliance is not something that can be universally applied to any group solely based on physical characteristics such as hair color. Additionally, dismissing Margaret's claim on the basis of her natural hair color is an example of an ad hominem fallacy, which is an attempt to undermine an argument by attacking the character or background of the person making it instead of addressing the content of the argument itself.