False. "The majority of X are Y" does not imply that any particular X is Y.

I don't have data for Signal. I use it extensively. Even setting aside that the American legal system makes everyone a criminal several times a day so that the laws can be selectively enforced against anyone who becomes a target, I have no data on whether the majority of Signal users are criminals, but given that criminals have significantly higher interest in secure communications than the general population it wouldn't shock me if evidence came out that it was the case.