moderationist
/ˌmɒdəˈreɪʃ(ə)nɪst/ /ˌmɒdəˈreɪʃənɪst/noun
An advocate of moderation; specifically a person who is in favour of moderate drinking, as opposed to total abstinence.
Origin
Late 18th century; earliest use found in Thomas Twining (bap. 1734, d. 1804), classical scholar and translator. From moderation + -ist.