TL;DR if an already existing topic is created click "report to moderators" and report it, as simple as that.
I used to do this back when the gambling section had more redundant threads, but I got discouraged when most of my reports got marked as bad. At that time, they would usually delete these threads, but nowadays, most threads would only get locked or moved to a different board.
Not just only in gambling board alone, I have reported some threads in the past that turned out to be some bad report despite the face that the post was a spam or in the wrong board.
The other alternative is to discourage others from posting in these threads because they will be pushed back to the next pages very fast since we have a lot of active threads in the gambling discussion board.
That would have been a pleasant idea only that forum members will never abide by it. If a new gambling addiction thread is created I bet that those that are currently supporting the motion that gambling addiction thread are becoming too muc will be the first to make a reply there reather than to click on the report button or direct the Op to the already existing thread ( if both cases are similar) take a look at this thread:
https://bitcointalk.org/index.php?topic=5456913.0 it was creatd yesterday admist of all the complaints of such type of thread and it already has more than one page yet we're complaining of too much addiction threads. If we are not going to do anything about it then we can as well stop complaining.