The "I'll believe only what I want to believe and I will completely ignore/denounce any hard evidence to the contrary" is so depressingly familiar and is guaranteed to end in tears.
Accept the world the way it is and negotiate intelligently with IAG management and you will get a better outcome.
There is a fundamental lack of understanding in this thread as to how IAG works. IAG itself is a holding/management company and the individual member airlines are separate businesses with their own credit identities that have to stand on their own feet without any cross guarantees by IAG. Member airlines do not "steal" routes from each other. IAG's job is to oversee the overall strategy and maximisation of merger synergies.
For what it's worth Iberia has issued a statement rubbishing SEPLA's claims, not that some seem minded to listen to anything that doesn't equate with their worldview.
Noticias - Iberia
Oh, and if Iberia pilots are so convinced their are victims of a vast conspiracy in which IAG's auditors are complicit in engaging in false accounting there is absolutely nothing stopping Iberia's unions hiring their own firm of accountants to review Iberia's accounts under a non-disclosure agreement.