The "you must stay on Twitter forever because I fear change" guys would've never survived the Y2K era. All our friends were on 19 different message boards and chat services and all of those sites were killed/reborn every four months. Sites aren't real. Only posters are real
"The Left has no choice but to stay on Twitter" can be best understood as the writer saying "I worked very hard to get all my followers on Twitter and I don't want to have to start all over again somewhere else"