Well that "guy" you just spoke on fb is clearly a prick. However not every reenactor or events are based on that mindset.
Blue Gray Alliance are openly about females as a combative soldier, however they require that the females must attempt their best to make themselves appear as a man as possible because during the war, there were quite a few account of females converting their looks to a man to serve and successfully.
For example,
Also there are videos of great events with historical standards set high but females are still noticeable on the battlefield.
like this [youtube]http://www.youtube.com/watch?v=G8BQe0vBJdc[/youtube]
at 1:42 hell even before you play it, thats a female on the right..... and she did took part of battle as a nurse or whatever.
Also in my unit, we have a female in our rank who did fight a few battle with us.