“Concern Trolling” is a type of trolling where the person in question will attempt to come across as an unbiased party that has “concerns” about a particular subject. For example, on a blog post about a particular political party, a Concern Troll might post something like this:
I am a long-time supporter of Party X. However, their handling of this health bill has made me a bit disillusioned. I will probably vote for Party Y next year, even though I dislike them.
In reality, the above poster has never supported Party X. Instead, he or she is a long-time supporter of Party Y.
People who use Concern Trolling do so because they know that they will probably be shut down if they come across as an ideologue or a loyal supporter of something. They also know that there is a better chance that Concern Trolling will convert other people to their side.
A few months ago, a new user posted a comment on a Facebook group for skeptics. The man in question knew that the members of this group did not believe in conspiracy theories. He also knew that he would be ignored or shut-down if he attempted to push his conspiracy theories in an open manner. So, instead of just coming out and saying that he thought 9/11 was an inside job, he decided to play the role of an unbiased observer. i.e. He attempted to come across as a skeptic that was “puzzled” about certain elements of the official story (he had great lines, such as “Just trying to clear something up in my mind”).
Unfortunately for him, his attempt to Concern Troll the group ended as soon as somebody realized that they had seen him posting conspiracy links on another page. i.e. He wasn’t just trying to clear things up. He was actually a fully-blown supporter of the idea that 9/11 was an inside job.
After being exposed, he launched an angry tirade against members of the group and left.