In answer to your
specific question, "reasonable articulable suspicion" does not mean, as
your question implies, that an officer has to articulate that suspicion
to the armed citizen.
"Articulable" in that context means that it can
be articulated (such as in a court proceeding), not that it actually is
articulated to the citizen. In short, the officer does not have to
prove to you that he has valid reasons for disarming you -- he just has
to be able to express those valid reasons to a judge if necessary.
If an officer requests your weapon on a consensual basis
(something that is not really likely to happen), you have no obligation
to comply. If the officer demands your weapon under force of law, you
aren't really going to have much choice.
My experience is that 1) the
officer will have plenty of backup on the scene, unless it's just not
possible; 2) the officer will order you to put your hands in the air or
otherwise make it clear you are being commanded and detained and not
consensually asked; and 3) the officer will physically take your weapon
himself, as opposed to asking you to hand it to him (or at the very
least he will ask you to hand it slowly and carefully with a two-finger
pinch of the very end of the grips).