I have always been ambivalent at best about reenacting.  When done well I suppose it can be a useful learning tool.  A demonstration of Civil War artillery carried out by guys in jeans and sneakers would look pretty silly for one thing.  Moreover, everyone deserves a hobby and a chance to relax and have fun however he or she prefers.  Personally I avoid reenacting for the same reason I avoid historical fiction.  The past is another place and any attempt to recreate it is futile.  We should do everything we can to understand the past on its own terms; we just shouldn’t succumb to the conceit that can return to it.  My biggest concern, though, is that some reenactors may be hiding behind the minutiae of camp life, clothing, and whatnot as a means to avoid the tough stuff of history.  Glenn W. LaFantasie has a thought provoking piece on the subject.