I always think of trolls as saddo people, emotional leeches if you like. There are some very clever ones about, and inevitably people get taken in, and give (often sterling) advice and support.
Then along comes a poster on the thread, crying 'Troll, troll', instead of simply reporting. The danger of this is accusing genuine posters of trolling. I've noticed this before, but not really paid much attention beyond giving trollhunter a mental catsbumface. However, a RL friend is currently feeling very upset and vulnerable following being called a troll herself (CRS, regarding giving personal info about herself on a recently notorious thread), and as she has given much of herself in other threads, is taking basically being called a liar hard, as she has been so supported here, and in turn has supported others. Those others may now, in turn, feel taken in.
AIBU to believe trollhunters appear to be more keen on being able to say 'I told you so' than the feelings of possibly innocent people they are accusing?