In the 2000s, when used in a
lawyer-created public apology, a word that demonstrates that the person concerned (
eg. a sportsperson) knew their actions would be wrong before they acted, do not
regret their actions for one second since, and are annoyed they got caught out and are forced to make a public apology to keep their career going.
When used by another authority such as their coach, using 'unacceptable' implies the latter is also annoyed that the former got caught out, is forced to make a public apology and that the mud
sticks to the authority by association.
I realise my use of performance-enhancing
drugs to allow me to win
games was unacceptable. I would like to unreservedly apologize to the
public, my team and my sponsors, for my actions.