Yes, you do indeed always react instinctively to a RA. Which is fine and dandy in an evironment with all traffic squawking Mode C, but here in the UK it isn't mandatory even to carry a transponder at all at lower levels in Class G airspace. So, if you react to a RA against one aircraft which is squawking, you might actually endanger another which isn't. As well as yourself, perhaps.
TCAS was never intended for use outside controlled airspace, in fact originally it was for use in terminal airspace only, IIRC. So to use it in TA/RA mode in the 'open FIR' positively invites needless RAs against wholly legitimate VFR traffic - as well as giving no protection whatsoever from non-squawking traffic.