When I first visited Stoneleigh a couple of years ago I was perturbed by the number of nazi uniforms being worn by visitors.
To put this into context, in Scotland, we don't have militaria shows and fairs like Stoneliegh and W&P so you could say it was part culture shock.
I have no problems with re enactors however I did find the odd one or two dressed as concentration camp guards to be particularly disturbing.
On one hand, a couple dressing up as camp guards and calling their dog 'Fritz' could be seen as offensive, however, it could be argued that most people involved in atrocities like the Holocaust were just ordinary people 'just doing their job'. (The banality of evil)
Good re enactors should be able to (hopefully) make the ordinary person stop and think.
*Apologies if this post is a bit rambling*