That's not a cliche, that's a systematic failure in an entire subgenre of HP fics -- the failure of the author to account for Dumbledore's actions when constructing his incredibly creative and exciting version of the Wizarding World and not changing Dumbledore's history to match it. Either there should be astute and believable reasons that Dumbledore would act the same under different conditions, or you need to change Dumbldore's history and plot role.
-- Bob
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Then the horns kicked in...
...and my shoes began to squeak.
-- Bob
---------
Then the horns kicked in...
...and my shoes began to squeak.