How bad does downvoting have to be before it's not allowed?

There's a thread where everything I say has been downvoted. This amounts to a loss of 14 karma. Because of the pattern of downvotes, it appears it's all from one person. I highly doubt that that I'm saying things ten times as worse in this thread than I am anywhere else, so it seems that I've been downvoted for expressing an unpopular view.