LOS ANGELES — Buried in the anti-Semitic manifesto of the 19-year-old man who recently opened fire in a synagogue near San Diego is a sentence in which he blames Jews for “causing many to fall into sin with their role in peddling pornography.”

It’s just one line in John Earnest’s 4,000-word screed, but the phrase offers a glimpse into a specific brand of antipathy that has been brewing in the dark corners of the web.

Amid the recent surge in hate crimes and shootings, some of the suspects in racist attacks and their supporters have invoked the societal ills caused by pornography in manifestos or online forums.

White nationalists, misogynistic clubs and online forums have also drawn a connection between pornography and anti-Semitism. Many of the adherents appear to be young men who blame the prevalence of pornography online for their own struggles and what they perceive as society’s decline.