Bristle worms typically do not kill corals, anemone, clams, etc. They are actually very good scavengers and do a decent job at keeping our substrate & rock clean. If an aquarium has a modest # of them living in it, it is completely fine and even beneficial.
Bristle worms have a bad rap for numerous reasons. The biggest reason is that when something dies in our aquarium, we discover a dead animal with bristle worms on it. Naturally the assumption is that the bristle worm is the culprit. Very rarely is this the case. Bristle worms do not attack & eat healthy tissue. When we see bristle worms eating a dead animal, they are doing their job, they are scavengers.
There are a few causes of large populations of bristle worms. A common cause is the purchase of live rock that was infested with them. Poorly maintained live rock holding tanks is typical in most pest shops. These dirty environments are perfect breeding grounds for bristle worms. Likewise is the case in our home aquariums, if there is a lot of food available, a modest population of bristle worms can turn into a large population.
As per removing them, there are traps specifically for them that work fairly well. just putting out bait at night can bring them out and they can easily be caught (netted) and removed. There are some fish that eat them also, like the Arabian pseudochromis (pseudochromis dutoiti) has the reputation of eating small ones.
Probably the best, long term defense against them is to simply keep the aquarium very clean. You can not have a large, nuisance population of bristle worms unless there is a lot of food (read; dirty aquarium) present to support their population. Keep the substrate very clean, vacuum it regularly, do weekly to bi weekly water changes, keep filter pads rinsed weekly, feed the tank sparingly, etc. These maintenance methods will benefit just about every aspect of your aquarium and keep nuisance pests to a minimum. (not just bristle worms)
Hope this helps...Joel