The arrogance of an pseudo-adoptionist suggesting that Catholicism is not Christianity...its amazing.
Go read CCC 841 and figure out if you're really worshipping Yahweh or Allah... Rome says that if you're a Catholic, you're "adore[ing] the same, merciful God" as Muslims. And we KNOW they do NOT worship Yahweh. If you profess to be worshipping Yahweh, then you're at odds with Rome and may be poorly catechized. If you cling to Rome's teachings, well, then, we're talking about two different objects of worship.
Catholicism is a denomination just like the Methodists or Baptists or Presbyterians or any other denomination -- Christianity is FOLLOWING CHRIST. Christianity not Catholicanity. There are, no doubt, Christians among Catholics just as there are Christians among the other denominations. But *being* Catholic does NOT make you a Christian... no more than standing in a garage makes you a car (h/t to Billy Graham, I believe).
So, really, the only arrogance I see here, and have seen in general, is that practiced by Roman Catholicism.
Hoss