TCAS targets displayed on our NDs don't have the accuracy of an SSR or ADS-B. So even if the aircraft you see is in the same position as TCAS target, it might not be the only aircraft there or might not be the actual traffic at all.
Obviously there are times when it might be a good idea to disregard TCAS (RA below 900ft in case of equipment quirks as somebody described, etc.), but to disregard it in cruise, just because you think you might be visual with the correct aircraft. Also, TCAS is not a 2.5g manuever, nor does require any abrupt flight control movement - just a gentle pitch up/down to satisfy RA requirements. This of course takes into account that both aircraft compy with RA orders - otherwise the RA commands might require much higher ROD/ROC.
Not to be picky, but the FAA circular has no implication here. EU-registered aircraft operating in European airspace by an EU AOC holder. It is also Boeing procedure to follow any RAs unless below 1000ft or that visual contact requires other action (i.e. you follow RA and it looks something bad will happen anyway).
ACAS II overview | Eurocontrol:
Pilots are required to immediately comply with all RAs, even if the RAs are contrary to ATC clearances or instructions, unless doing so would endanger the aircraft.