Clearly a flawed conclusion. For the result of their experiment they deduced what they wanted it to say. Because we can easily say that the effect is not "dislike attacking" but other effects:
- shy people more afraid to give their opinion not knowing that others have done the same.
- the feature feeling useless, as even if you dislike, you might thing that you click will worth nothing as no one will see it.
Imagine if you were voting for something but no one will give you the result of the votation.
Also, strangely they did not do the same experiment with the "like" button to see if there was not a "like attack".
So when I see something like that, I'm thinking that they are now in the dominant position where they don't have to care about their users anymore...