I don’t know where you got that sincerity has an ulterior motive since you either are sincere or not.
This is actually about appealing to a persons higher nature to perform a sleight of hand.
Lets say that somebody takes your wallet, you angrily demand of him/her to give you what is yours, If that person fails to give you your wallet because he finds your tone offensive, then you’ve been duped.
If he gives it to you immediately, yet takes offense and tries to guilt you into something else, then you’re possibly being duped.
Yes you can catch more flies with honey than you can with vinegar, but being denied what is due to you BECAUSE you don’t give honey is called being a serf.
