To be enthusiastic about something, and to attempt to share that enthusiasm with others; to promote.
To preach any ideology to those who have not yet been converted to it.
Coordinate term: proselytize
To tell people about (a particular branch of) Christianity, especially in order to convert them; to preach the gospel to.
Hypernym: proselytize
To persuade someone, gain someone's support, or make someone understand the truth or validity of something.