Of course it would be personal preference. But the way it is now people still upvote certain articles based on personal preference, but there is no way for the

Of course it would be personal preference. But the way it is now people still upvote certain articles based on personal preference, but there is no way for the "opposite" group to express their personal preference by downvoting, thereby potentially cancelling out the people who upvote out of personal preference. So you get a sort of upward bias for these emotionally loaded articles. I'm not saying that allowing downvoting will perfectly cancel this out, but at least it may do so to a certain degree.