Before the crowd at an April 10 hearing of the Senate Judiciary Committee's Subcommittee on the Constitution, Senator Ted Cruz, R-Texas, displayed a billboard containing a tweet of a Mother Teresa quote, "Abortion is profoundly anti-woman. Three quarters of its victims are women: Half the babies and all the mothers."

Alongside the quote was a picture of the saint, smiling.

Then Cruz, the subcommittee's chairman, asked expert witness Carlos Monje of Twitter's public policy team a simple question: "Is this hate speech?"

The graphic in question was posted to Twitter on March 8 by Marjorie Dannenfelser, president of the Susan B Anthony List. The national pro-life organisation had intended it to run as a promoted ad, but Twitter ensured that it never saw the light of day by removing it immediately.