That's what I call them too.

I have started muting more and more of them. If they're really offensive (and start trawling thru my tweets) I'll block 'em, but I love muting because they're then just howling into the abyss.

If you think about it - when you answer a comment online, and it gets no response, how do you feel? It's no different for them. They exist for attention, so they must be starved of it.