My philosophy on my actions taken on Steem and Steemit is that whatever they are, the actions should be meant to increase the value of both. In this case, downvoting you for presenting an idea that I believe would lower the value of Steemit and thus my stake in Steem is a rational action in line with the philosophy of maximizing value.
In other words, I believe Steem should not be paying the users who seek to lower its value, whether they do it intentionally or not. As a moderate stakeholder in Steem as a whole, I have a voice (albeit smaller than many) in where the rewards go. And I'll use a downvote when I see it to be valuable to Steem as a whole.