On historical aircraft, no problem. Indeed, sanitizing history is pretty dangerous, IMHO. When one oohs and ahs over a FW-190, for example, it's good to remember who's toolbox it belonged to. The same for replicas.
Everything else, just weird. If someone wants to paint Nazi crap all over their Cessna 172 that's their call...but don't expect any praise from me. Especially if they're from Illinois. One has to wonder why in the hell any American would glorify the 3rd Reich is beyond me.
That said, I am completely hypocritical on painting aircraft in Allied schemes. Go for it. We are, after all, the good guys.
That's why I stick to WWI aircraft, back when we all hated and killed each other simply because it was the thing to do. Even then, I built a French plane because there were no American WWI scouts, only French planes flown by Americans.
[edit]
I found out after I built my plane that home building is actually something that's happened before, which explained why everyone over there (my parents immigrated, so my distant relations are in Germany) was so casual about it.
Here's my great uncles and their glider shortly before the war:
Bear in mind that this glider was at the 1936 Olympics as part of the demonstration team, and if one wanted a tow the symbol on the front did not hurt.
If I could find this glider and restored it, the nose decal would be on it, along with the Olympic rings.
If I were building a similar glider, or recreating it, probably not.