Always follow the RA.
he had RA with, which he did not follow, as he had the traffic in sight. Was he right in your opinion?
No he was absolutely wrong.
The visual assessment of traffic can be misleading. At high altitude, it is difficult to assess the range and heading of traffic as well as its relative height. At low altitude, the heavy aircraft attitude at low speed makes it difficult to assess whether it is climbing or descending.
• Visual acquisition does not provide any information about the intent of other traffic.
• The traffic in visual contact may not be the threat that triggers the RA. A visual manoeuvre relative to the wrong visual traffic may degrade the situation against the real threat.
Eurocontrol stuff via skybrary