Trying too hard to change someone's mind can push them the other way

When a persuasive message feels too forceful, or comes from a source people distrust, it can shift attitudes in the opposite direction from the one intended. Psychologists Carl Hovland, Irving Janis and Harold Kelley documented and named this 'boomerang effect' while studying wartime and post-war persuasion campaigns at Yale. It's one reason that heavy-handed anti-drug or anti-smoking ads sometimes make the behaviour more appealing to teenagers, not less.

— Carl I. Hovland, Irving L. Janis, Harold H. Kelley, Communication and Persuasion: Psychological Studies of Opinion Change — Yale University Press, 1953
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