Think I have to agree with Fruitbat and my understanding of his point of view.
To claim to have the full understanding of any investigations the Iberia crew have already conducted is arrogant and thoroughly unproffessional to attempt to name and shame them here. As you say at no time did you see any tech crew check his aircraft this doesnt mean it didnt happen. Indeed I would hope you were concentrating on your own aircraft and procedures. You were unsure whether he was sufficiently deiced and you voiced your concern, fair enough, good call even. BUt thats where it ends. He is the Captain of his aircraft its his decision, to assume a lack of professionalism because you disagree with that is wrong especially when not party to any discussions held in a cockpit you were not in.
As for comments that although he made it back safely doesnt mean it was the right decision, I'm afraid we have to assume it does. We cannot start offering what ifs and buts to justify our arguements based on no knowledge other than that placed here by someone who may be miffed that he looked stupid on the radio when he was ignored.