This is fantastic Political Satire; we need to be able use Satire in the correct way and Waititi did just that. If you think this movie is offensive here is Satires definition:
Satire 1 a literary work holding up human vices and follies to ridicule or scorn 2 trenchant wit, irony, or sarcasm used to expose and discredit vice or folly
Satire 1 a literary work holding up human vices and follies to ridicule or scorn 2 trenchant wit, irony, or sarcasm used to expose and discredit vice or folly