It depends a bit on the vintage of the film you are looking at.
Ultimately, an RA is an advisory. Since manufacturers and regulatory authorities recognise that TCAS can not be aware of every possible circumstance, ultimate authority regarding following an RA has to devolve to the commander on the spot.
It is certainly possible to envisage circumstances where following an RA might actually be more hazardous that not doing so. However, simply feeling that the RA is not necessary does not qualify as such a circumstance.
Many operators do have procedures that allow an RA to be disregarded in the event of visual contact and no confliction, however opinions have hardened against such procedures.
I agree with your A320 acquaintance. In fact, there was an incident in the USA several years ago which was a good learning point (for those that paid attention!). Very paraphrased, it went like this.
- Aircraft has 2 RAs in quick succession against 2 different aircraft.
- First RA is followed, intruder misses by a fair horizontal distance anyway. Crew get visual with first intruder as it passes abeam them.
- Crew get second RA, against a (thus far) unspotted second intruder. They consider the RA to be not needed as they assume it is related to the aircraft they can see passing clear. However, they wisely elect to follow it anyway.
- They do spot second intruder as it intersects with them horizontally, missing purely by TCAS generated vertical seperation.
- Crew become paid up members of the 'TCAS is a good thing' society!
CPB