The danger of ignoring an RA is that you assume that the aircraft you can see is the one which triggered the TCAS. The Tcas may be warning of another aircraft which you have not seen.
Quite, but with one aircraft on the scope at the correct bearing and no other traffic, it was safe to assume as you can only get a warning from traffic that shows.
Exactly my point regarding having a human on the flight deck . . . Also my point that if there is doubt, then there is no doubt.