Rubbish. O'Neill and Keane are always mouthing off in the press when they don't like a situation with a player. Koeman was quite within his rights to decry the decision of an international manager to take a player, who's wages and the bulk of his rehab we fund, and risk his physical well being for his own short term goals.
I am assuming you are an Irishman as I cannot believe anyone taking an objective view of this could come to the conclusion that you have drawn. Everton and McCarthy lose in this situation and the only possible winners are the Irish national team, who contribute nothing to the players development in football terms, his financial security (in terms of stability with his current employer or his ability to attract a future employer) or his ongoing health.
Koeman was right to say what he did and I hope he keeps publicly calling out international managers on this issue.