protester (n.)

• apostate
• brawler
• defendant
• demurrer
• diehard
• disputant
• dissenter
• dissident
• litigant
• naysayer
• negativist
• nonconformist
• objector
• obstructionist
• opposer
• plaintiff
• protestant
• quarreler
• recusant
• resister
• scrapper
• sectarian
• sectary
• separatist
• wrangler