JERUSALEM—Growing up in evangelical Christian churches, Caleb Fitzpatrick learned quickly to be a steadfast supporter of Israel. From a young age, Mr. Fitzpatrick said, he was taught that Benjamin Netanyahu, Israel’s prime minister, “was a hero” and that “Christians are supposed to back Israel on everything.”

But the Tampa, Fla., native, who just finished his junior year at Liberty University, an evangelical school, has become critical of Israel for what he says is its mistreatment of Palestinians.

“Human...