You might find this explanation answers your question.
'Offensive' is a noun here.
Interested in Language
I know what "charm offensive" means.
It is when someone tries to look better in the eyes of others by doing good stuff.
So the person is trying to "charm" others by his/her deeds.
But how come the word "offensive" came to the expression?
Doesn't it have a negative meaning?
Is it here a noun or an adjective?
I've checked the link.
But why was offensive used here?
If we say "Charm Attitude" it would sound acceptable, but what is offensive about trying to look good the eye of people?
Was "offensive" used because the expression has a negative meaning? I mean it's a form of cheating or lying or what?
I see. Thanks