Well, Din, the problem had the German War only been a colonisation aim, probably it would not be considered offensive any more. But it was associated to organised mass-murder and thus wearing the sign of the Nazi cross is associated not to territorial expansion, but to massive, brutal and organised murder.
But isn't that post war villification? The Nazis (to make the distiction from the ordinary Germans) did cause horrendous bloodshed, death etc. But so did the Soviets, so did the Brits, the Americans, China, Japan, Australia etc etc etc. There is little anti-Patton propergander, or Le May, or Harris, yet mention the name Himmler and everybody gets the creeps.
The German issue is that all the efforts after WWI have been forever tarnished by Nazi-ism. I am just not sure that is entirely right.
As mentioned above, we do (did) know a WWII reenactor who is particularly interested in Germany. He has an astonishing personal libary, which is very creepy. But why is it creepy? Why is this the big issue. Why not Soviet or Chinese communism? Why not carpet bombing of Japan? why not the Manhatton project?
One of the really facinating things to see in re-enactment is the respect given to people who reenact WWII by the real participents. As long at the kit is 100% accurate, they really do have respect for them, including thoseswho dress as Germans. It is facinating to see old soldiers who last met as opponants at D-Day or in the mountains of Italy, and how they now get on. There is very much a feeling of 'please don't forget what we did' from them, and they mean it. Even the SS verteren I met a few years ago, who refused to admit that what he did was wrong and that they failed because of the Russian mongrel (his words). But he thanked the guy who was dressed as a Fallchemjager for not letting what he did become forgotten. In Germany, he said he could not admit what he was part of even to his grandchildren. I found that sad.
And several people have mentioned being shown the tattos from concentration camps by old Jew's who then tell their grandchildren 'this is what we faced, this is what we looked at everyday, don't you forget'. It is apparently quite moveing.
Another interesting story, one which may be an urban myth, was of a group who had dressed as French Resistance fighters. They were approached by a woman who had been branded a collaberator after the war, and she launched such a tirade against them because of what had happened to her.
I am not sure what I am trying to say here, except this. Most of the people who find it offensive to depict WWII were not part of it. They are our generations, post war baby boomers who grew up on war stories without real understanding of what it meant to take part. Even those that still hate the otherside, after all these decades still take comfort that it is not forgotten in case it happens again.
Having said that, I did get the creeps when I saw a group portraying East German border guards. They went over in 1989 and bought the flags, uniforms and everything before it was thrown out.