Vindicator

(n.) One who vindicates; one who justifies or maintains.

Thesaurus Entries

Nemesis, advocate, apologete, apologist, apologizer, avenger, champion, defender, guard, justifier, paladin, pleader, proponent, protector, revanchist, successful advocate, supporter, the Erinyes, the Eumenides, the Furies, upholder, whitewasher