I was having an allergic reaction to something the other day, and I typed in the symptoms into Google, just to see what I could find.
And I found a discussion group where someone posted the same symptoms. And some troll posted a response, "Sounds like Lung Cancer, you'd better get it checked out!"
Now, of course, this is idiotic. But a lot of people who are decent and honest don't even grasp the concept of the troll. Trolls are sniveling teens giggling behind a computer keyboard, thinking they are clever. They are not.
So, some people actually responded, "Lung Cancer, what makes you say that?" - actually taking the person at face value.
If you see a troll, just kill them. On sight. Run them down with your car. Shoot them in the head. Stomp them to death. Repeat as necessary.
People like that are just, well, evil. And not in the fun way.