"I'm not going to defend infanticide," said Fiona Watson of Survival International, a group that defends the rights of native tribes all over the world. "But I think you have to understand," she said, that in the context of Indian culture, "it's not considered murder."
"In fact," she said, "it's often considered something which is a kind thing to do. If you have somebody who is born into your community who is not going to survive, who is very badly deformed and you are an indigenous people who are living deep in the jungle, you don't have access to medical care, that is the kindest thing to do."
Critics say the missionaries' claim of 200 baby killings a year is seriously overstating the problem.
"Infanticide is quite rare and it's dying out," Watson said.
For the missionaries, "this is part of a strategy to justify their presence on indigenous lands," Vaz said.
He and activists like Watson are particularly offended by the "Hakani" movie, which they call racist.
"Community actions are taken out of the cultural context and portray the Indians as savages, barbarians," he said.
At a time when Brazil's Indian tribes are being forced off their land or killed by ranchers, miners and loggers, Watson says the infanticide issue is a destructive distraction.
She argues, in fact, that evangelical missionaries have emerged as perhaps the greatest threat to the Indians' survival.
"I think they are doing a huge amount of harm," Watson said. "They are destroying people's beliefs."
Watson says that when the Indians' traditional faiths are erased, it destroys their cultures, which have remained self-sufficient for hundreds if not thousands of years.
"I have seen that," she said, "where a once proud people end up subdued, dependent upon people, because they have lost their beliefs."
Vaz recently completed an investigation into Youth With a Mission. His report accuses the group of "hiding their intent to evangelize" and bribing tribe members with tools and medicine to get them to listen to the gospel.
The report, without elaboration, accuses the missionaries of slavery, illegally taking blood samples from Indians and illegally removing Indian children from their homes.
Braulia Ribeira, who runs the group's operations in the Amazon, denies the allegations.
"I think they threw as many accusations as they could, hoping that at least one of them would stick," she said.
"They are trying to take the focus off the problems," Suzuki said. "Children are being killed, hundreds, in very cruel ways, but the government is trying to distract people and say, 'No, it's not the problem. The problem is the missionaries.'"
The missionaries deny that they are using infanticide as a smoke screen for efforts to convert Indians. Group members, including Marcia and Edson Suzuki, often live with tribes for decades, learning their ancient languages and providing health care and education. Despite their religious orientation, Ribeira says, they do not proselytize.
"Our main mission," she said, "is to provide access to means of survival."
However, at one site where the group is working, deep in the jungle near Porto Velho, an Indian girl wears a Jesus T-shirt.
Francisca Irving, one of the missionaries working there, freely admits to preaching the gospel to Indians.
"Yes, we teach Jesus," she said. "I would lie if I told you we didn't talk about Jesus."
The legislative push against infanticide is gaining steam in the Brazilian legislature. One house of the Brazilian legislature has passed a bill to allow children whose lives are "at risk due to cultural practices" to be removed from their homes.
Meanwhile, Vaz says the Department of Indian Affairs is developing a policy.
"Infanticide is a serious issue, which needs to be discussed," he said. But, he added, "this is not a discussion that must only be seen through the Christian perspective."
CLICK HERE to read the Suzuki's response to the "Nightline" report.