Speech is sending and receiving information.
Speech/information needs to be processed/filtered/analyzed. People may not be equipped to deal with certain information - hence we try to manage it externally and internally.
Suppressing from of information starts at early, at childhood. We try not bombard our children with all the information indiscriminately. We curate and provide age appropriate information to ensure optimal development and growth.
Once a person becomes adult they are supposed to gather and process information on their own. However, even as adults we are susceptible to deception. Our judgement can be fooled, feeling can override our logic.
In conclusion, I think there's a need for curation of the information/speech. Not forbidding it outright, but certainly to help humans discern facts from fiction, for example.