Yeah, but then you may have people that want to discuss the spoiler and it might defeat the purpose. I think a separate Spoiler Only section of the forum might be a great idea. If there is a way to create a new section, similar to the WWE and TNA sections, but remove the thread preview when you are looking at the forum's front page, that would be ideal. Maybe even replace the preview with a simple warning stating "WARNING: SPOILERS".
There are many other forums on the net that has this available, DarkUFO is a great example of this. They have a spoiler section for the show Lost, and they ban anyone that posts spoilers anywhere else but that section. There are going to be a large number of people who DO want to discuss spoilers, so why not give them a forum to do so?
Credit to Uncle Sam