Senator ted cruz and others are worried about both censorship and the spread of misinformation.
And some industry watchers agree the legislation – known as Section 230 – needs to be revisited.
“[It] allows digital businesses to let users post things but then not be responsible for the consequences, even when they’re amplifying or dampening that speech,” Prof Fiona Scott Morton, of Yale University, told the BBC’s Tech Tent podcast.
“That’s very much a publishing kind of function – and newspapers have very different responsibilities.
“So we have a bit of a loophole that I think is not working well for our society.”
Mr Zuckerberg told politicians he supported changes to the rule “to make sure it’s working”.
What is Section 230?
Section 230 is the main legal protection preventing social networks being sued.
It means websites themselves are not generally responsible for illegal or offensive things users post on them.
They are treated as neutral middlemen – like newspaper sellers rather than the editors that decide what goes in the paper.
Originally seen as a way to protect internet providers such as BT or Comcast, it has become the main shield for huge sites such as Facebook, Twitter and YouTube, which cannot possibly review every post from their users before publication.
But politicians say Section 230 is outdated.
Democrats take issue with the spread of lies online without consequences for the sites.
Republicans say big tech is using its moderation powers to censor people it does not agree with – making editorial calls rather than staying neutral.
And both sides agree they want to see the social networks held accountable.
Mr Dorsey told the committee Section 230 “is the most important law protecting internet speech” and its abolition “will remove speech from the internet”.
But he found himself faced with pointed questions over the implementation of Twitter’s policies about what it removed or labelled misinformation.
Asked why Twitter would label a post from US President Donald Trump about the security of mail-in ballots but leave posts by Iran’s Ayatollah Ali Khamenei that threatened violence against Israel unlabelled, Mr Dorsey replied the Iranian leader’s tweets were considered “sabre rattling”, which did not violate its terms of service.
Mr Dorsey also found himself facing questions from Republican senators over Twitter’s limiting of a New York Post article about Joe Biden’s son.
“The New York Post isn’t just some random guy tweeting,” Republican Ted Cruz said.
“Who the hell elected you and who put you in charge of what the media are allowed to report and what the American people are allowed to hear?”
Both President Trump and his election rival Joe Biden have called for the removal of Section 230, though for different reasons.
But some Democrats used their time to criticise the entire hearing, positioned so close to the election, as a political ploy.
“I’ve been an advocate of reform of Section 230 for literally 15 years,” senator Richard Blumenthal told the committee, referring to his time as a state attorney general.
“But frankly I am appalled that my Republican colleagues are holding this hearing literally days before an election, when they seem to want to bully and browbeat the platforms here to try and tilt them towards President Trump’s behaviour.
“The timing seems inexplicable.”
His colleague Brian Schatz, refusing to ask any questions of the three chief executives, “because this is nonsense”, said: “What is happening here is a scar on this committee and the United States Senate.
“We have to call this hearing what it is.
“It’s a sham.”
SOURCE : BBC