Three things that politicians are great at, and Donald Trump is the best at, are lying, deflecting, and covering up.
Sunshine is the best antiseptic.
If he had simply reported to these guys that he was in the chat, they would have deleted him from the chat, kept using Signal exposing us to ongoing security risks, and then lied about it when he reported on it after the fact. He appears to have done exactly the right thing. They would have been chanting the Trump mantra "fake new, fake news, fake news" with a dead look in their eyes, had he handled it differently.
This is why many companies, and maybe the government, hire white hack hackers, to uncover their vulnerabilities before they are exploited by bad actors. And the thing about bad actors is that they never expose, just exploit. By exposing the incompetence here, the reporter has done the right thing to prevent others from exploiting. Again he is owed a debt of gratitude. Not censorship.
You are proposing censorship, which makes no sense to me given your prior proclamations that you were being censored and now it would stop.