I think the main reason we have a downvote button is to prevent content from gaining traction which the community deems to be unsatisfactory or breaks our moral code. I also believe that we have a downvote button to be fair with having an upvote button. 

I personally would not use the downvote button since I believe that everyone has a right to what they want to say, even if I don't agree with it. However, the only time I would use the button is if I found something very offensive I didn't want inside of the Hive community.