You remove the whole Papal infallibility thing and all the rest of the arguing will come to an end outside of internet boards.If so, why no union before 1870? (when papal infallibility was first officially proclaimed dogma)
Indeed. They'd need to ditch supremacy, infallibility, universal jurisdiction and anything else that they've added to the papacy since the first millennium. Of course if they did do that and he once again was seen as simply the Patriarch of Rome given primacy by the councils, that really should put an end to it because they'd have to concede that Rome was in the wrong the whole time - which is exactly why they'll never do it.
The authority of the Pope, his individual, unilateral authority over the whole of the church, is the overwhelming problem, along with the doctrine of his infallibility too. The biggest problem with the matter of the "filioque" is that the Pope superseded the work of two Ecumenical Synods (Councils), and modified the language of the "Symbol of Faith," the "Creed," language that is based in scripture.
P.S. The Roman Catholic doctrine of the Immaculate Conception of the Mother of God, is also a matter of substantial dispute, among Eastern Orthodox Christians, not noted above from what I saw.