The problem is, whatever the term may have meant once upon a time, it is now used as a general pejorative for anyone whom the author disagrees with (as long as the target is even marginally perceived as a conservative and/or a Republican). Since the term has really lost its meaning through corruption in common usage, I have no problem discarding it.
Going back to Godwin’s law, it does not deny that Hitler or the Nazis exist, it’s just recognizes the cheap and lazy tactic of calling your opponent a “Nazi” or comparing them to Hitler, especially when there are better comparisons to use.
That may often be the case...but when discussing the invasion of Iraq....it was most certainly people who could accurately be called neoconservative who had been writing about and advocating it since the mid-1990's...although I would agree with you that Mulsine is incorrect when he refers to GWB as a neocon.
Bringing up Hitler means that one doesn't have a real argument and that one's just trying to force a conclusion. Using the word "neocon" is a lot different. The person who does is trying to categorize a group. He or she may not have found the right word, but it's not like they don't have an argument or are trying to force a conclusion that facts don't support.
Once, when neoconservative notions were only ideas, there were many self-described "neoconservatives." Now that those ideas have become policy and have consequences people are trying to back away from the label. That's their prerogative, but it's not true that people who still use the term have automatically lost the argument.