Facebook said it would block references to the alleged whistleblower’s name and photos under its policy against “coordinating harm,” which prohibits “outing of witness, informant or activist.” YouTube announced a similar action.

But Twitter said it would allow naming the individual who Trump supporters say is the whistleblower — as well as photos — as long as the information doesn’t include personal contact information. So Twitter has become the go-to platform for vicious attacks on the whistleblower that supporters say could endanger the individual’s safety.

The former head of the U.S. Office of Government Ethics, Walter Shaub, asked Saturday why Twitter was failing to suspend accounts of people trying to “get the whistleblower killed by naming the person they think it is.” He added that Twitter will be “largely responsible if anything happens to this person.”