I disagree with the notion you must respond to a RA even if you have the other aircraft in sight. Not in sight, absolutely, but in sight means just that. I've sat and watched departures climbing out of airports while on downwind for another runway. I had them in sight before the traffic call, had them in sight before the TA and had them in sight before the RA. If the course looks like it might converge, act accordingly. If however you receive one because of the large threat envelope of the TCAS when clearly there's no threat, as in the other aircraft couldn't hit you if he wanted to, then you are making the situation worse.
I've heard the counter arguments of those who propose acting ALL the time, I don't buy it.
Yes, my companies sop's allow us to disregard the RA if the threat aircraft is in sight, it also says we must follow it if the flight paths appear to merge.