Zuckerberg knows that the dislike button would many people stop from posting their trash. Perhaps the will just rename the like button to whatever fits the context best based on the posted event (probably needs to be categorized).
Few people post a news article to facebook because they want a healthy debate on it, they do it because they want to get general agreement from their friends and family. The people who go on and start arguments in the comments are pretty universally hated in my experience. Nobody likes scrolling through the news feed and seeing drama drama drama.