I also received a negative one a few days ago, but I didn't attach any importance to it because we have to take into account that such things can happen completely by accident. Now that I read that someone is obviously on the warpath and doing negative karma to everyone, I hope that the administration will detect him and deny him that privilege.
Getting a single negative karma is normal. Probably someone gave it by mistake. Or they probably did not like your post. But, if you continue to get negative karma from time to time and you don't remember writing such posts that may result from this, then there is something wrong, and someone is abusing their karma power.
In the case of AB de Royse777, he does not really write too many posts on the forum except for writing in his campaign threads. So, there is not much scope to judge his post's quality and send negative karma. I strongly believe it's just because someone does not like his decision and decides to abuse the power they have.