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.
Does not meet the standards of The Earl of Lemongrab
“This castle is in unacceptable condition. Unacceptable!!!!!!!!!!!!!!!!!!”
unacceptable: define #2
Something extremely inappropriate.
Your mother’s extreme amount of cooch hair is unacceptable.
unacceptable: define #3
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.
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.