They mean professional journalists, those who report news for a living and have at least one formal press credential.

Translated into tech:

They mean professional programmers, those who write code for a living and have at least one formal git repository.

That is meaningless from a legal standpoint. Press credentials are not a real thing with any official weight. And if someone reports news as a volunteer for a non-profit organization are they not a journalist?

They are a real thing and bring significant privileges in some jurisdictions. In some of them, press credential is actually government issued and yes, they tend to exclude volunteer journalists. It does not mean volunteer journalism is illegal, rather that volunteer journalists do not confer the same privilege as a professional one.

I am so thankful to live in the USA where anyone can be a journalist and no government credentials are needed.

My intention was more to express the idea that, when society is discussing an instance of violence like a riot or police brutality, people need to be able to see the violence so that they can decided for themselves what happened.

My concern is that if violent content is scrubbed from social media, then it will become too easy for thought leaders (journalists, politicians, celebrities, etc.) to simply tell people what happened without any way for them to confirm it.