The Guardian reports they unleashed Ms. Marvel, a Pakistani American superhero from Marvel comics.
The group splashed images of Ms. Marvel on the ads along with cartoon bubbles proclaiming “Calling All Bigotry Busters,” “Stamp Out Racism” and “Free Speech Isn’t a License to Spread Hate”.
The protest was endorsed by Ms Marvel comic co-creator and writer G Willow Wilson who likened it to a freedom of speech “call and response” and summarized her sentiments with the simple tweet “spread love.”
The use of comics in social justices responses has a long tradition. You can read about that and the origins of Ms. Marvel in the Guardian.