I think Schlafly is misrepresenting what Calles did in Mexico. He wasn’t going after Christians generally but just after the Catholic Church. I’ve read that some American Protestant churches were fine with what he was doing, thinking that this would give them an opportunity to convert Mexicans to their denominations. Calles was an honored visitor to the White House while Coolidge was President.
Read a book, or see the Andy Garcia movie about the Vivo Chriso Reys.