The threats began last December, when Drexel University professor George Ciccariello-Maher tweeted that all he wanted for Christmas was white genocide.
This week, he resigned, after a year of enduring unrelenting harassment and death threats for his controversial tweets, he said.
"After a year of harassment by right-wing, white supremacist media outlets and internet mobs, after death threats and threats of violence directed against me and my family, my situation has become unsustainable," he wrote in a statement on Facebook.
Dozens of incidents of harassment against professors have been reported on college campuses in the past year, with African-American professors among those most targeted, according to the AAUP.