They're schismatics and heretics.
They jacked a boatload (if you'll pardon the expression) of Catholic "swag" and jumped said boat long ago.
With all due sir, they're about as relevant as Protestants or any other pack of heretics and schismatics.
I'm arguing with some of them about the filioque, eventhough I provide quotes from church fathers that state the Holy Spirit proceeds from both the Father and the Son they are still obstinate in their heresy
here's the last response they gave
In short: there is a difference between eternal procession and temporal procession. When Orthodox Fathers state that the Spirit "proceeds from the Father and the Son," they are speaking about temporal procession, not eternal procession. The Creed is speaking about eternal procession, so "and the Son" is not appropriate in the Creed. The ancient patristic consensus (Rome and all of the East) was to NOT have the Filioque in the Creed. The East remained faithful to that ancient patristic consensus, whereas the West perverted the Catholic consensus and fell away from the Catholic Church. If you do not clearly understand the difference between eternal and temporal procession, then you will misunderstand the entire issue. Please read the following carefully:
SAINT GREGORY PALAMAS AND THE COUNCIL OF 1351 IN CONSTANTINOPLE (THE "NINTH EcuмENICAL" COUNCIL)
[The Holy Spirit] proceeds from the Father. He is co-beginningless with the Father and the Son as being outside time, but not without beginning, as Himself also
having the Father as root, source, and cause, not as generated, but as proceeding; for He also came forth from the Father before all ages immutably and impassibly, not by generation, but by procession, being indivisible from the Father and the Son, as
proceeding from the Father and resting in the Son, having union without confusion and division without division. He is God and is Himself from God, not one thing insofar as He is God, but another insofar as He is the Paraclete; He is the self-subsistent Spirit,
proceeding from the Father and sent, that is manifested, through the Son, the cause of all that came into being, since They were perfected in Him; the same equal in honor with both the Father and the Son, without ingenerateness and generation. He was
sent from the Son to His own disciples, that is, He was manifested. For how otherwise would He Who is not separated from Him be sent by Him? How otherwise, pray tell, would He come Who is everywhere? Wherefore,
He is sent not only from the Son, but also from the Father and through the Son; and He comes from Himself when He is being manifested. For the sending, that is
the manifestation, of the Spirit is a common action. He is manifested, not according to essence, for no one has ever either seen or declared the nature of God, but according to
the grace, power, and energy that is common to the Father, the Son, and the Spirit. For the hypostasis of each, and whatever belongs to it, is peculiar to each of these. Not only is the super-essential Essence, which is entirely nameless, inexpressible, and incapable of participation, since it is above every name, expression, and participation, common to Them all, but also
the grace, the power, the energy, the radiance, the kingdom, and the incorruption, and in general everything according to which God communicates and is united by grace with both holy angels and holy men. Departing from His simplicity neither on account of the distinction and difference of the hypostases, nor on account of the distinction and variety of powers and energies, we thus have one all-powerful God in one Deity [θεότης,
theótēs]. For neither from perfect hypostases, could there ever come about any composition, nor could what is potential, because it has power or powers, ever truly be called composite by reason of potentiality itself.