Passage Summary: If you think ads are bad just because they change what people like, you'd have to think art classes are bad too; since art classes are fine, that specific criticism of advertising doesn't hold up.

Conclusion: The fact that advertising changes consumer preferences does not, by itself, make it socially harmful.

Reasoning: The author compares advertising to music and art classes, noting that while both change people's preferences, the latter are considered beneficial rather than harmful.

Analysis: This argument uses a counter-example to undermine a specific criticism of advertising. By showing that another socially acceptable activity (art classes) shares the same trait (changing preferences), the author demonstrates that this trait cannot be the sole reason for calling something 'socially pernicious.' It's a classic 'if A then B' logic check where the author shows that B isn't always true when A is present. Look for a completion that reflects this logical debunking of the critics' premise.