“my personal opinion with no filters” is all it means. Has nothing to do with honesty or truth. Just mere opinion of a single person.
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We are talking about honesty but you refer to opinions. “Brutal honesty” is unfiltered opinion.
HONESTY – just plain old honesty; is related to HONOR, virtue, just, elegance, show respect to, beauty, etc.
The notion of “brutal honesty” is a silly hack, implanting “opinion” where opinion need not be.
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