I guess I just come from a very different place--maybe all those years as a protester in the '60s have too deeply instilled in me the concept of individual freedom.
IMHO only
posts containing personal attacks and/or vulgarity, or those posts obviously intended to incite and/or annoy, should ever be deleted. The only situation where I think it would be appropriate to close down an entire thread is when there is a heated battle going on between or among a small number of posters who are posting (attacks upon one another) faster than the mopderator can delete them--in that case just lock it down.
If a thread is simply boring or overdone, it will die of lack of interest and should be given the opportunity to do so--that may be an even better lesson to the poster than closing the thread.
We each have a different perspective on just about everything and this is mine on moderation. It is neither right nor wrong, it simply is.