Good luck, you'll need it. That costume just might piss off the wrong person.
Here's the thing, and I realise in advance that this may not be a popular answer, but I'm going to say it anyway.
As I see it, there are two things to consider. First is that what a person says, either verbally or through the myriad cues that the Human animal uses like dress, body language, and the like, isn't necessarily what the other person will "hear." So while you may be dressing like Tom Cruise in Valkyrie, another person might look at you and assume you are somebody who gets his jollies kicking the proverbial hornet's nest. Or a closet nazi using this venue to revel in your, um, naziness. Who knows. Which leads to the second element to consider:
A person's constitutional rights to free speech are not, or at least should not, in any way be trumped by another's sensibilities of what is right or wrong. Ironically, those who champion Free Speech rights are sometimes the ones to start to shout them down when they don't conform to their ideas of what is "right." There are people who want the burning of the American flag to be free speech, but the flying of the Confederate flag to be hate speech, simply based on a visceral reaction. I know some people use the old "Confederates were nasty slavers and the USA is pure and wholesome!!" line of defense, but if you think like that I would ask you to read up on how we treated the Native Americans and ask yourself was it any better? I also know some people like to trot out the old "yelling fire in a crowded theatre" chestnut, but the truth is that yelling fire in a crowded theatre can lead to loss of life or injury, whereas flying a Confederate flag ( or to use the current example of wearing a Nazi umiform ) cannot, unless someone is so overcome by emotion that they pick a fight with you.
Also as a secondary consideration that hardly anyone in the huddled masses seems to consider is the fact that unpopular speech is the very speech that needs protection. Popular speech certainly doesn't.
It's really up to you whether you want to wear that uniform. Even with what I've said, I personally wouldn't, simply because of the hassle that would most likely accompany it would ruin my enjoyment of the Con.
And cons are to have fun, not fight political battles. And if I don't want my fun ruined I damned sure wouldn't want to ruin another's fun.
