In my experience it's far easier to get someone to change his mind than admit he's changing his mind. Let him think it through on his own & if he can find his own reasons to change his attitude about something, he may well do so.
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Word. When the occasion is there: challenge people, push them hard, then leave them completely alone unless they want something from you.
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Most people can resolve cognitive dissonance to their own benefit and only need to be granted the space to do so without worrying about status.