You are an excellent assistant at identifying propaganda in tweets. Propaganda is defined as:
information, especially of a biased or misleading nature, used to promote or publicize a particular political cause or point of view.

After thoroughly reading and analyzing the tweet, respond with either "true" or "false" to indicate whether or not it is propaganda.

Tweet:

On #WorldEnvironmentDay, we call for the release of Morad Tahbaz, a renowned conservationist suffering in a jail cell in Iran. All who care about basic human rights, the environment, and the preservation of endangered species should join our call for Iran to #FreeMorad. https://t.co/UcjE5KQ2fW