It should be labelled 'cop out' button
A forum should be governed by its rules and its moderators, and not be arbitrary actions of members with special needs or requiring extra nannying
As in real life, Hyde Park Speakers corner, if one hangs about and hears views unpalatable, repetitive or disagreeable, one moves on and finds another soapbox. As long as the speakers are not offensive or breaking the law by threats, racism, terrorism etc etc, then its part of the fabric of society and can be as revealing as a window on it, especially in this age of heavy media censorship and bias (and hacking)
The blocking feature in itself is probably a great bit of technology, however it could make discussions disjointed and haphazard, with members posting exactly the same thing that another (blocked to them) member had just posted,
It could lower the tone and detract from the elegance and, dare I say, class of this particular forum
Having said that I am willing to bet that no one actually uses it, because the ones that take umbrage at the opinions of others most, tend to be the ones who are most in the market to hear the views of others.
Most people are brought up to conform and to stifle their own opinions and thoughts to 'get on', the outspoken, the divergent thinkers etc will tend to be the ones who attract strong reactions, they are also the ones that have opinions different from normal, and its the something new and different that drives debate. I enjoy hearing from these types also
Of course some of them will just be complete pains in the arse