I am pleased to announce that Verizon has now reversed that policy.
According to The New York Times, Verizon spokesperson Jeffrey Nelson said that the previous decision to block NARAL's text messages was an "isolated incident" and "an incorrect interpretation of a dusty internal policy" that "was designed to ward against communications such as anonymous hate messaging and adult materials sent to children."
To me that seems like a lame excuse, given that you have to actively subscribe to NARAL's text messages. They're not sent anonymously or unsolicited.
Nevertheless, this is good news for Verizon Wireless subscribers, and for the First Amendment in general.