Nobody has been stopped from speaking their minds.
The subject of the criticism has just decided it no longer wants to facilitate this criticism and they should be free to the extent outlined in the contract.
they should be free to the extent outlined in the contract.
Only if the contract is valid. I don't think you can sign away your right to speak your mind about an airline in order to be allowed on a flight. That would be unlikely to stand up in court in the UK.
The subject of the criticism has just decided it no longer wants to facilitate this criticism and they should be free to the extent outlined in the contract.