Earlier quoted context omitted.
In much the same way that even laws do not apply to anything said in Congress, because the power to control political debate is the power to control government. https://en.wikipedia.org/wiki/Speech_or_Debate_Clause
Except wasn't that clause to stop the Executive Branch (and anyone else) from using the machinery of the state to interfere with Congress? Not really about freedom of speech, rather keeping Congress independent from outside control. A lot of former British colonies have the same principle, dating from 1688/1689: https://www.parliament.nz/en/visit-and-learn/how-parliament-...
Exactly what's at stake here. Keeping the government independent from outside control by those who happen to control the means of communication.