Twitter said Monday that the president’s tweets didn’t violate its policies, but independent researchers who study social media said they struggled to see why. The platform bars attacks on people on the basis of their race, ethnicity or national origin…

“It’s clear that this stuff violates their rules. They should at least label it,” said researcher Heidi Beirich, director of the Southern Poverty Law Center’s Intelligence Project. “I think Twitter should decide what their community standards are and enforce them, even when it’s Trump.”

A Twitter spokesman, Brandon Borrman, said Monday, “The tweets in question are not in violation of the Twitter Rules.”

He declined to elaborate on why the tweets did not violate company policies.