Freedom of thought is the freedom of the invididueal to hold or consider a fact, viewpoint a fact , viewpoint and thought. This freedom is considered one of human rights and ensured by international human rights law such as International Covenant on Civil and Political Rights
Bertrand Russel did not promote freedom of speech but for the few elite. He was third generation empire who in his book from 1931, The Scientific Outlook, where he outlined two types of education, one for the elite (his class) and one for the common people. This is what he said about those who does not want to comply with the elite... "the rulers will reluctantly conclude that there is nothing to be done with him except to send him the lethal chamber before his ill-diceplined intelligence has had time to spread revolt. This will be a painful duty by the rulers but I think they will shrink from perfoming it", end quote.