Phrases, sayings,
What do they really mean?
"To be perfectly honest" "To be absolutely honest"
So the rest of the time, without this prefix you are not.
"In all due respect"
You hear this all the time in The House of Commons, usually just before a put down, some disparaging disingenuous comment.
"In my humble opinion".
Which Charles Dickens's, Uriah Heep character made so famous, in point are always far from humble.