I love military costumes to death, but I do not beleive anywhere in the general public outside of reenactments are like, Nazi uniforms ever a good idea. I am cosplaying a character with a blatant SS inspired uniform and I will not wear it outside of convention grounds and go where it could be seen by the general public. It's not that I personally would be offended by people who wear the uniforms but, "just because they are cool" is an insensitive reason. Unless it's for reenactment or a specific character (even then, dont leave the con XD), I think it's pretty insensitive to go around wearing something that offends many people. If you're out and about in cosplay, wearing a nazi or nazi inspired uniform, the general onlooker will have NO idea that you are just pretending.
We had something happen where we were at a mall in Hetalia cosplay, and my friend told someone when they asked her what she was, that she was WW2 Germany (just lie, people. Don't even say you represent a country XD). I'm not certailn, but their accents sounded alot like someone I knew from Israel. The lady went and told her companion and she yelled back "So you hate Jews?"
While we thought it was all hilarious at the time, my friend was mortified, and later I sorta reeled over the fact that it possibly made those people insanely uncomfortable. I agree, the stuff is still "too soon". It still hits close to home for many people who are still affected by it years later even if they weren't alive during the war itself.
The only other uniforms I could think that should be avoided, probably anything from WW2 Japan, as well as the Red army uniforms. Avoid anything with the hammer and sickle too. I found out from a Chinese friend who also cosplays China, the red arm bands are beyond offensive, and she will not wear it out in public. I dunno about Italy, I guess it depends on where you live. I don't think most people know what their uniforms looked like :/
As far as WW2 US and British uniforms go, meh. No one seems to care. I've seen people eat out in public dressed as the Basterds and no one was batting eyes at them anymore then the Naruto cosplayers. Since none of it is associated with anything offensive, it seems fine to do. People will probably just assume you are in a reenactment automatically.
I think it's all just common sense, don't be out of your way to be offensive. It doesn't matter if the outfit ISN'T a Nazi uniform, if it LOOKS like it, close enough.
No one really bats an eye at the Hellsing cosplayers at conventions anymore (as long as you stay IN the convention), it's only the times we see people dressing up as SS Germany or Prussia that we feel a bit concerned. It's all in very poor taste after that seig heiling crap last year.
+AREI - THE COSPLAYING CACTUS+