Newsom called remarks by board president Joseph Komrosky offensive and ignorant.
"This isn't Texas or Florida. In the Golden State, our kids have the freedom to learn," Newsom tweeted. "Congrats Mr. Komrosky you have our attention. Stay tuned."
Newsom's tweet was in reference to Komrosky and board member Danny Gonzalez calling slain gay rights activist Harvey Milk a "pedophile."
Komrosky and Gonzalez responded to Newsom during a town hall-style meeting with supporters at 412 Church.
Last month, they and board member Jennifer Wiersma voted 3-2, opposing new social studies curriculum due to the lack of parental input.
Opponents say that was a smokescreen.
"What they're not bothering to tell people is that it's in the teacher's manual, not the children's book," Gia Rueda of Temecula said. "They're basically disapproving the textbooks because they have a problem with someone who happens to be gay."
Temecula Valley teachers and their supporters are rallying the community to give their input on the new textbooks ahead of next week's school board meeting. They say without approval, students could be left without textbooks and the school district would be in violation of the Williams Act.
"This could cost the district over $4 million because they don't want a gay man mentioned in the teacher's manual of supplemental reading material," Rueda said.
Gonzalez says he's working with state education officials on finding the necessary textbooks.
"Our students and teachers will have what they need for the start of the year, and I continue to work through this daily," Gonzalez said.
Even so, state Attorney General Rob Bonta and Newsom are demanding answers.
"California is closely watching the actions of malicious actors seeking to ban books, whitewash history, and demonize the LGBTQ+ community in Temecula and across the state," Newsom said in a statement. "If the law is violated, there will be repercussions."
Komrosky and Gonzalez did not answer questions from the media following their press conference. The next school board meeting will be held next Tuesday in Temecula.