The Hollywood screenwriter behind Pirates of the Caribbean and Shrek is at the center of a social media firestorm after using a racial slur to defend parents who choose not to vaccinate their children.

In response to a fellow screenwriter who called for an increase in vaccination participation, producer and screenwriter Terry Rossio wrote, “My heart goes out to all the parents of vaccine damaged children, who have to not only endure the sadness of their loss, but also the vitriol of ill-informed and insensitive people (such as those here). Anti-Vax is equivalent to calling someone a n***** and makes as little sense.”

Rossio spelled out the epithet.

When the writer who started the conversation asked Rossio to “please never come on my feed with the n word again,” Rossio doubled down, arguing in a thread that the stigma faced by African-Americans is similar to that faced by those who refuse to vaccinate their children out of scientifically discredited fears of autism.

Rossio’s many critics—the tweet had more than a thousand replies—included fellow screenwriter Jeffrey Grubb, who responded acidly: “God, this is such a good point. I remember how American founders and citizens enslaved vaccine skeptics for decades. And then, even after freeing them, the government enshrined laws to marginalize vaccine deniers and to deny them wealth and opportunity. That’s just history.”

Another Twitter user replied to Rossio with the announcement that his comment inspired him to donate $25 to a nonprofit that vaccinates children around the world.

Rossio, whose credits include Aladdin and The Lone Ranger, as well as the upcoming feature adaptation of Johnny Quest, did not respond to a request for comment. Two years ago, he reportedly acquired the rights to a book by Dr. Andrew Wakefield, whose work linking vaccines to autism has been repudiated in the scientific community.

“Dr. Wakefield is clearly a polarizing figure, reviled by the general public yet also revered by many. The details and drama surrounding his life are even more remarkable than generally known,” Rossio said at the time.