No. An insult is an insult. You can't divide it into pieces. And the preposition which follows is
to meaning
directed at. Some examples :
Lack of action by police over Birmingham pub bombings is an insult to the people of the city Today's ANC motion is an insult to the people of KwaZulu-Natal.
In this case, as you have a passive verb you could also let the preposition depend on that and use
by, but of course the meaning changes - ie you are saying that the people consider it an insult:
They were known as afrancesados, a term considered an insult by the people ...