So now we can deduce what this is really about.

Translators are civil servants with security clearances, not reporters. When the leaders of Germany and Brazil have a meeting, they may say things they don't intend for China and everyone else to know about, and it isn't the translator's job to report what was said to the media. Unless they've witnessed something on the scale of criminality that they need to act as a whistleblower (in which case they wouldn't need anyone's permission), they should never be telling anyone what happened in the room since their job is to keep those secrets.

The media are fully aware of that, but they're being disingenuous and pretending that allowing a diplomatic translator to act as a media witness is a request anyone is likely to grant. Then Trump predictably responds to that by removing the translator from the room, so now they're complaining about that instead.