"Musket, who decides whether views are 'different to yours' or, alternatively, 'have no place in 21st century society'? Surely it's a matter of opinion, and that's where the problem lies."

Surely though it is a matter of opinion up to a point only. There are lines that can be crossed where an opinion becomes offensive and people may feel the need to speak out or disassociate themselves form the other person. For instance we were visiitng my wife's friend, and her husband, when he came out with the following.

When speaking about me having platonic female friends he said "I can see no reason to be friends with a woman unless I was getting to f*** her" Now this wasn't said as a joke it was deadly serious and said in the company of both our wives.

Then he went on "You know there are three things I hate, "Pakis, single-mothers" then he looked round pointedly at his wife and continued "and fat people".

So he was expressing opinions, and I can live with people who differ in opinion from me, but I didn't really want to socialise further with someone who in my mind held pretty horrible viewpoints.

It is the same on-line. There is a line where one's opinions become unacceptable. The vast bulk of people have an idea of where the line should be and it may differ from person to person but it is still there.