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.
Actually, most of the time they are trying to force a conclusion by labeling the other side with a "dirty" name. Only in rare cases does it really refer to neconservatism, and then, the author would be better using the full word rather than the shortened version.
But this is getting way off the tracks... my original comments were intended to be lighthearted humor, not a deep philosophical discussion. :/