The Australian Vaccination Network (AVN), a citizen group advocating parental choice in whether children should be vaccinated, has come under an extraordinary attack by advocates of vaccination. Controversies over vaccination involve both disagreements about scientific matters, such as the effectiveness of vaccination to prevent disease, and clashes of values, including compulsion versus free choice. To help understand the attack on the AVN, I give an overview of the nature of scientific controversies, including the roles of evidence, vested interests, solutions, paradigms and methods of debate. I analyse a formal complaint against the AVN to highlight the assumptions underlying the anti-AVN position. I describe some of the methods used to attack the AVN: unsupported claims, formal complaints, and harassment. Finally, I discuss tactics for opposing the attack.