Anyone's ability to broadcast on Twitter is only as far as the system dynamics of Twitter and its users allows them. Retweeting is not some pure expression of speech that needs to be "free", it is limited already shaped and limited by all kinds of incentives and technological particularities (character limit, anyone?).

I think media should function to encourage speech that balances social and individual utility. That is, speech that has important protection from powerful actors like the government and CEOs, but also that incentivizes true and useful information, in all the nuance that is necessary to actually understand the world. (Obviously entertainment is useful as well.)

But engaging lies are not a form of speech I value, and equating the current operation, or slightly-more-permissive version of it, of an overwhelmingly constructed forum (i.e. Twitter and it's retweet system) with "free" speech doesn't make much sense.