A crude search of the COCA and the BNC shows that it is we is just over nine times more frequent in American English than it is us, but only about five and a half times more frequent in British English. There may thus be a certain amount of instability in the use of the first person plural personal pronoun, as indeed there is in all personal pronouns, and in particular in the first person singular.
My intuition is that nominative forms (I, he, she, we, they) are preferred when they are postmodified in some way, but that the accusative forms (me, him, us, them) are preferred when they are not (you and it being invariable). On those grounds, it might be advisable to use It is we here, and in any case fewer people are likely to object to it.
There, of course, ways of avoiding any difficulty altogether, and you have suggested one of them. Another alternative is something like:
Who are the real culprits? We are, the ignorant, apathetic people of