Trolling is a fact of life on these forums. But starting witch hunts reflects poorly on all of us.
Effective trolling will raise an issue that people are genuinely concerned about, in such a way as to provoke a defensive emotional response. If I feel someone is subtly trolling in this way, I find the most effective response is to offer a polite, reasoned argument that addresses the raised concerns. This approach is beneficial to any onlooker who shares those concerns, it avoids playing into the hands of the suspected troll. It also avoids needless accusations, which is especially important if my suspicions are wrong and the person is just raising a genuine concern.
When you have politely answered and they keep coming with the same "question" on purpose what do you do ? Because that's what they do, they create a false issue and repeat it till it's "true".
The logic for dealing with trolls remains the same whether they are raising a question for the first time or the
nth time: If you flame them, you lose. Every time a troll is answered with patient educated responses, they lose.
Trolls lose interest if they don't get the right reaction -- in fact it works against their agenda if the community shows consistently mature responses that directly address the issues raised. On the other hand, they'll be sure to stick around if they know they're ruffling feathers.
We use the generic term "troll" but they are not the common trolls just wanting to annoy people for the fun of it. Most of them here have an agenda, they are motivated more or less directly by money. Therefore, they don't lose interest.