Funny thing that no-one seems to be discussing the actual incident, namely an Argentinian aircraft that is told to visually follow the Iberia (number 2) but follows the easyJet (number 1) instead causing a conflict with the Iberia. I'm sure it was all in Spanish, but that should not be a factor here. I always thought it was dangerous in dense civil airspace to be told by ATC to follow or maintain own separation with other aircraft.
With regards to AMS, we tend to give them far more credit than they deserve. Their operation is slick and honestly they seem to do a good job, but sometimes they are too slick and hence not so good. Funny enough I have never had any major trouble in Spain, but in Amsterdam I have had my share of interesting events (vectored into the parallel arrivals, total ATC breakdown due to a single CB)!