I'm just tired of the signal pollution, and would like to be able to use karma to honestly appraise the worth of my articles and posts, without seeing 80% of my downvotes come in chunks that correspond precisely to how many posts I've made since the last massive downvote spree.
EDIT to add data points:
Spurious downvoting stopped soon after I named a particular individual (not ALL downvoting stopped, but the downvotes I got all seemed on-the-level.)
One block of potentially spurious downvoting occurred approximately one week ago, but then karma patterns returned to expected levels. I consider this block dubious, because it reasonably matches what I'd expect to see if someone noticed several of my posts together and disagreed with all of them, and did not match the usual pattern of starting with the earliest or latest post that I had made and downvoting everything (it downvoted all posts in a few threads, but not in other threads), so I'm just adding for completeness.
Spurious, indiscriminate downvoting started up again approximately half an hour ago on Sunday (12/1/2013), around noon MDT.
Edit: And now on Tuesday, 12/3/2013, at 10 AM, I'm watching my karma go down again... about 30 points so far.
Edit: And now on Saturday, 12/14/2013, at 2 PM, I'm watching my karma go down again... about 15 points so far, at a rate of about 1-2 points per second.
I've experienced the same thing. I used to be annoyed when my karma suddenly dropped by 10 points, but more recently I had a 100 point drop within a time span of less than an hour. I'm guessing I'm growing more susceptible to it as my post count increases. I honestly don't know what to do about this kind of thing, so for now I've decided to simply abstain from caring too much.
It would be nice if there were some sort of forum rule that prevented people from downvoting a single person too many times. That's the best solution I can see right now, though it's not perfect.
In your case, the vast majority of your comments are highly political, and frankly, unnecessarily emotional. It is far more likely therefore that people are simply reading the comments threads you are in, and downvoting comments as they read them.