As annoying as it is, the reality is that followers provide independence. If a reporter has a following, they can be more independent against corporate media power. Demanding reporters “delete their Twitter” is to cede to corporations, who will never leave Twitter. A better start to this would be to encourage journalists to join Mastodon *too* to build and diversify their audience, and to get them to report on Mastodon itself to get more folks here.
Constructive things to say to journalists: join Mastodon, encourage your audience to have their conversations here, report on Mastodon, add Mastodon to your news org bio, make a video explaining how to use Mastodon, ask lawmakers if they will be joining Mastodon
Not helpful: You are a fascist just like Elon Musk for not immediately deleting your Twitter and giving up the audience you spent 15 years building. It’s all or nothing, right now.

Definitely.

It is also true that as a journalist, if you've ever DM'd with a source or shared your phone # with Twitter, you / your employer are currently at risk of harm on the current twitter.

That is an insecure environment and you're actively being hunted and targeted over there.