Trust me, you do not want or need a dislike button.
I've seen people on facebook lobbying for this for years, but there's a very simple reason why they will never ever do it... It is far to easy for a "dislike" to be misconstrued. Yes, the person might correctly take it as affirming a negative post, but they could just as easily take it to mean that the person dislikes them or what they have to say (not to mention that the reader might in fact be trying to insult them with a dislike).
On the other hand, while I think it's weird that some people will "like" a negative post, you don't ever think of that as being rude. So if someone dislikes something, then that's what the comments are for, to explain why they feel that way.
You don't want to leave it up to your reader to interpret a "dislike", because it could easily offend them to where they say "forget this place, I'm not going to go where people dislike what I have to say".
lol....i told them that. I personally feel that the dislike button is a negative feature to have on a social network
Glad to see there are plenty more that realize this...
Beyond just not "liking" something you dislike, I'd even go as far as to say that forcing them to express their displeasure in the comments instead can in many cases be a good thing. No matter whether they affirm what that person has to say ("that stinks"), or they provide a reason for debate, if it's done by reasonable and intelligent people (or even just 1 knowledgeable person taking on false misconceptions) can be a HUGE source of traffic, as people line up to get in their 2 cents or read the intellectual debate that insues. (Also, trainwreck threads can be huge traffic boosters too, but that's not something I recommend subjecting your serious readers to).
Of course there are plenty of instances where disagreement can be negative too, but no more than "disliking" something without stating any particular reason why you do... Obviously that's only likely to create animosity and misunderstanding.