Grammatical gender is different from actual gender. Nouns have to have gender, but their grammatical gender may not be the same as the gender of the thing described, if it has any. In French, some examples are (cribbed from the Web):
bébé "baby" is always masculine, even if the word is used to refer to a baby girl. Here is a list of words that behave in the same way:
Une vedette "a star" is always feminine.
Un guide "a guide" is always masculine.
Une personne "a person" is always feminine.
Une victime "a victim" is always feminine.

So saying "il est une victime" is perfectly grammatical and correct French.