SACRAMENTO, Calif. (AP) – A California bill that would sharply limit vaccination waivers after a Disneyland measles outbreak has generated such an acidic debate that the proposal’s author was under added security this week.

Authorities said wouldn’t specify the extra protections around state Sen. Richard Pan on Friday, but the level of anger over the measure has been clear.

Opponents have flooded the Capitol to stand up for parental rights, and images that compare Pan to Adolf Hitler have circulated online.

“Unfortunately, there is a sub-segment of the group that seems to want to engage in vitriol and intimidation and bullying in order to get their way,” said Pan, a Democratic pediatrician from Sacramento.

Sen. Carol Liu, chair of the Education Committee, which will hear the bill next week, said through a spokesman that the proposal has generated more calls to her office than any other this year, including measures immigration, doctor-assisted suicide and police shootings.

“It literally started the first day it was in the news, and it never stopped,” Robert Oaks, Liu’s spokesman, said.

Pan said he introduced the measure, Senate Bill 277, to limit inoculation waivers after a measles outbreak in December that started at Disneyland and sickened more than 100 people across the U.S. and in Mexico.

It would prevent parents from sending unvaccinated kids to school using waivers that cite religious or personal beliefs. Exemptions originally would have been available only for children with health problems but were recently expanded to include homeschoolers.

The plan has high-level support. Senate Leader Kevin de Leon, a Los Angeles Democrat, has signed on as a co-author.

But critics have turned out in force. Before the bill’s first legislative hearing this week, hundreds of opponents attended a rally that featured an appearance from Robert F. Kennedy Jr. During the hearing, one opponent threated to ask God to curse legislative supporters.

Vaccination foes have focused on potential risk factors, saying shots could be tainted or otherwise dangerous, and characterized the bill as outrageous government overreach. Opponents also worry about the drugs’ links to autism and other developmental diseases, even as supporters say such claims have been scientifically disproved.

Similar plans have been proposed and have failed in other states, including Washington and Oregon, where lawmakers received similar pushback.

“Some of it got pretty ugly,” said Paige Spence, aide to Oregon Democratic Sen. Elizabeth Steiner Hayward. “And I did my best to shield her from seeing any of it.”

Godwin’s Law specifies that as an online discussion grows longer, the probability of a comparison to Nazis or Hitler increases. This theory has been expanded to cover other forms of rhetoric.

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Associated Press writers Sheila V Kumar in Salem, Oregon, and Rachel La Corte in Olympia, Washington, contributed to this report.

Copyright 2015 The Associated Press.