The word or phrase (I prefer a word but a phrase will certainly do) I am looking for would describe someone who reacts without thinking and thus attacks something which is not the true source of the problem.
For example, there was a recent news story about a girl who dies from a heart attach shortly after drinking an energy drink, and in the news story her mom claims (without evidence) that her daughter's death was the result of drinking the energy drink. In the comments to the story, many people claimed that they also were sure her death was caused by energy drinks and that energy drinks should be banned. Now if we suppose for the sake of argument that the energy drink did not cause her cardiac arrest, what would we call these people calling for a major economic action without just cause to do so?
I think overreact may not be the best word here because I intend to convey that a person is not just overreacting but is also reacting towards the wrong thing.