[Viperfish]

That depends, are doing an impression of a real unit? Are you wearing unit patches? are you wearing the uniform properly? would you respect the wishes of a member in the unit you are impersonating if they asked you to fix something that they found disrespectful? Do you go around pretending you are in the unit you are impersonating? do you wear rank?

These are some of the questions you need to think about. if you are doing everything right then i see no real issues with it. if you are dressing up like 10th mountain and scroll "baby killer" across your helmet then your going to have a problem.