According to one dictionary definition the term “propaganda” should be understood as “information, ideas, opinions etc. propagated as a means of winning support for, or fomenting opposition to, a government, institution etc.” There is nothing here to indicate whether the information, ideas and opinions propagated need be true or false.
Thus, to take a simple example, the US occupation for more than a century of Cuban territory at Guantanamo Bay for use as a naval base, is a fact. To state that fact is to speak the truth. It is also a fact that the treaty by which the US came into possession of Guantanamo was imposed upon Cuba against the will of its people, with the threat that failure to accept it would result in the US occupation of the island. It is also a fact that since 1959 the Cuban government has refused to accept the rent from the US for Guantanamo, claiming, truthfully, that the territory housing the base belongs to Cuba and that the US has no legitimate right to be there. All of this factual information and the truthful expression of opinion by the Cuban government, most recently by President Raul Castro, demanding its return to Cuba, has been reiterated consistently for the past 56 years. The demand for the return of Guantanamo may be regarded as “winning support for” the Cuban government, or “fomenting opposition to” the US government. In that case such a demand could, according to the definition, be regarded as propaganda. It would, nevertheless be a just demand on the basis of a truthful presentation of the facts.