Truisms like this are taken as being true. However such assumtions are sometimes proved to be wrong. Words do hurt is what I read on the BBC news website.
This provides a really powerfull argument why we should not allow for all the baiting, the insults that are sadly part of many of the discussions on Wikipedia. The argument why unfettered abuse should be allowed is either freedom of speech or that nobody is really hurt. The last argument is patently untrue and with this new research it should even more clear. Freedom of speech does not mean that you are free to hurt others. Freedom is limited by the extend where your freedom meets the freedom of others.
Obviously there is a need to express unpopular points of view, what is at stake is particularly the manner in which an opinion is expressed.