LNT principles are just that, principles. They are not dogma. There is however a reason they exist, and it's not so people who adhere to them can be pretentious and preachy, or so that others can make sarcastic wisecracks.
Before I go further, I'd like to acknowledge the excellent point some have made about the paradox with hunting and taking stuff like antlers. I don't know the answer to this.
As for LNT, however, the questions one needs to ask before taking an action are:
Will this have an adverse effect on the plant or animal life, soil, water, geology, trail/campsite conditions, etc?
Will this affect the safety, health or enjoyment of future hikers?
I personally wouldn't take an antler, because if in fact they supply food for rodents, then that adversely affects rodents and their predators. If there's a chance someone (even one) other person might get to see the thing where it is, taking it will unquestionably make that person's experience less than it might have been. I also wouldn't be any happier with the thing than without it. If you think it's okay to take the thing, fine, take it. It doesn't make you evil. If you think I'm an uptight snob, fine, think away. This isn't about me.
It goes without saying that LNT is an imperfect practice. Life is an imperfect practice. Obviously, taking an antler or feather doesn't compare to littering, scratching your name on a summit rock or befouling a stream. But, if you're trying to rationalize something by saying "somebody else will do this anyway", "there's enough of this thing that I'm taking to go around", "so-and-so who I respect said it's okay" then maybe you should think twice.
What you really feel is important, and if you're rationalizing, maybe you don't really feel that good about it. Likewise if you become angry defending your actions. Conversely, if you really feel something's okay, then all the people in the world scolding you shouldn't make you feel bad about it. Principles (and happiness for that matter) must ultimately come from within, not from without. I'm not telling anyone to do something just because it says so in a book, just encouraging folks to think and feel.
Matt