For example, there is a tradition in many newsgroups and other Internet discussion forums that once [a comparison involving Nazis or Hitler] is made, the thread is finished and whoever mentioned the Nazis has automatically lost whatever debate was in progress. This principle is itself frequently referred to as Godwin's law. It is considered poor form to raise such a comparison arbitrarily with the motive of ending the thread. There is a widely recognized corollary that any such ulterior-motive invocation of Godwin's law will be unsuccessful.
I believe in free speech, and while I will defend their right to publish what they want, I do think it was an appalling decision to publish this.
Of course it should be possible to discuss Scotland's political history, including the role played by fascism, but it's entirely clear that Scotland on Sunday tried to imply that current nationalist politicians have fascist sympathies, which is both wrong and offensive.
I thought the unionists wanted to win the referendum by debating the pros and cons of independence. Alas, I was wrong. If they want to win by making Nazi slurs, all rational debate becomes impossible, which is exactly why Godwin's Law says that the debate ends here.