The first step in deciding what to do with an online troll is being able to identify them correctly. Many businesses use social media as another way to connect with consumers and field customer service needs. Which means complaints might get posted on your Facebook Wall and just because a customer is unhappy does not make them a troll.
The secret to more, better quality engagement is addressing consumer concerns on social. According to SocialBakers, brands who respond to at least 65% of audience questions on Facebook and/or Twitter receive 3.5 times more interactions than brands who respond less than that. For an industry so focused on engagement you think we would already have a handle on this, but the lack of quality customer care on social is shocking.