On February 20, Kass testified before a Washington state Senate committee in support of a measure that would eliminate personal and philosophical exemptions for childhood vaccinations. The move came amid a measles outbreak in the state that has infected 66 people—most of whom weren’t immunized—at the time of writing.

Kass—who won a Centers for Disease Control and Prevention immunization advocacy award in 2017—said that someone called him “a disgusting liar” in a hallway soon after the hearing, but this was nothing compared to the torrent of abuse that he found online several hours later, The Guardian reported.

When he logged onto Facebook, he noticed that profile was filled with one-star reviews from people who were calling him everything from a “disgrace” and a “pedophile” to a “Nazi pharma shill” and “scumbag shilling for infanticide.” The abuse continued even after he disabled the review feature, simply moving onto the comments section of his page.