New people (I am one of them as you will see if you go to my page) do not have the ability to down vote. From what I understand, the assumption is that by the time people get to the magic number (currently 500 I believe), they will have been here long enough to understand what to down vote.
I'd say the best recourse we have available is to set showdead to yes. I think it is quite obvious that we are not supposed to down vote things just because we disagree.
I can imagine a system like stack overflow where down voting a top level comment takes away like a tenth of a point from the down voter so if the down voter does nothing but down vote, they'll ultimately lose the privilege.
Regardless of where they're coming from, I know what you mean. I wish at the very least we'd see more questions or rebuttals or whatever being replied to the posters.