Originally posted by TransfinitumSounds like pretty good politics to me.
Your argument is inherently flawed, since Catholicism was and is the only church that Jesus Christ founded; therefore your argument that Catholicism is a branch of mainstream Christianity is absurd. In fact, the Church was re-named the Catholic Church in order to differentiate itself from heretical and schismatic sects (such as Eastern Orthodox). The reason that the Eastern Orthodox cannot possibly be the true Church (and the same applies with all other protestant denominations) is that they break from apostolic succession (every member of the Catholic Clergy can trace his ordination to Peter being ordained as the first pope of the Church, "And so I say to you, upon this rock I shall build my Church" (Matthew 16:18). Christ at this point is talking to Peter, and furthermore Peter as a name literally translates to "The Rock", so by using logical reasoning, it can be deduced that Peter was the first "Head" of the Church. From there he went around ordaining bishops and priests and now all priests and Catholic clergy can trace back to Peter. This is what gives them the true communion. The Eastern Orthodox broke from that succession when they schismed from the Church and instead of following the apostolic line, committed excommunicable heresy in ordaining bishops out of the line of apostolic succession through the Emperor and his officials; therefore they are one of the first "protestant" break-offs of Catholicism, not the other way around.