I reject the idea that everyone vaguely left of center - even random social media users - have to act and speak (type) as if their every word should be in service of the goal of electing Democrats, but also I observe that the notion is very selectively applied by people who embrace it.
"Activists" with policy agendas and must weigh everything carefully, while New York Times pundits with megaphones can just speak their pure thoughts unconcerned with the consequences!
They're free to do it, of course, but writing a bunch of pieces about how "the presumed Democratic nominee is too old for the job" will neither dissuade him nor help his re-election.
Again, my point is about how people with tangential associations with the Democratic party (if it all) are required to have extreme message discipline, while cable news "Democrats" are just going wild every day with this stuff.