I'm not voting you up or down, I'm replying you, so I guess I'm in the safe way :-)

Anyway, I just want to make the point that nobody should be punished by just downvoting. Sometimes you're interested in an article (or you think it is a good contribution, or that the tone is ok), others you're not. Therefore, sometimes you upvote, others you downvote. I wouldn't dare to say which level of downvoting is ok for each person, as this may vary depending on the user experience, knowledge or personality. Thus, I would be against establishing any kind of limitiation to how many downvotes a user may cast.

On the other side, I may agree with you about avoiding the use of votebots, but I feel they should be addressed separately: they're bad, weather they are used for downvoting or upvoting.