When threads start deteriorating into people saying hurtful things, and I get get complaints, I usually just delete anything that violates our
forum guidelines, and send a warning to the person who posted it. Depending on how bad it was and the person's history, sometimes we ban them.
But when the thread is quickly deteriorating into people posting angrily back and forth and it's clear that it will continue, I lock the thread. There are a few reasons for this.
Neither myself, nor the other mods, have the desire or time to monitor heated arguments that go back and forth all day.
These types of arguments usually don't get any better; they deteriorate into more name calling, and promote the type of activity we don't want here. Also, like Amp said, sometimes we just can't keep up with the rate of new posts and be able to evaluate things when that is going on.
To avoid getting your posts deleted or threads locked, think twice before you post, especially if you are angry at the person you're responding to. Try to get your point across without violating
forum guideline #1 "Treat Others on the Forum with Dignity and Respect."