Sorry I don't get your point. Steem has a voting mechanism to reward content. Upvotes add to the pending payout and downvotes remove from the pending payout. At the end of the seven days we get paid whatever payout the post has minus curation and beneficiaries. If the payout of the post is negative you receive zero payout not the negative payout. Therefore theft through downvotes is not possible. Nothing has been taken from you. I hope that clears things up.