You need to report the thread for the staff to be aware of the problem. They can't go through each thread, page-to-page, trying to clear way of trolls. I'm not sure what the like/dislike system did because I didn't use it as much but I doubt that the thread gets deleted/trashed. With the thread being there, without an original post, members will continue to spam the said thread which doesn't solve the problem. I don't think that the massive amount of dislikes notifies the staff of the problem either.
It all comes down to members reporting a thread that breaks the rules for it to be taken down. Posting in troll threads is what the trolls want so just report it and leave the thread to die out.