The Catholic Church is the Only True Church
[I'm sure the Orthodox might have a point or two they would want to contend.]
This is not a winnable argument, it is fractious and arrogant and about a generally welcome as a fart in a funeral.
Therefore, since I'm not at all interested in getting in a holy hand grenade tossing contest:
I am resolved to know nothing while I am here with you except Jesus Christ and Him crucified. (ref 1 Cor 2:2)
The wisest among us will simply say, "There they go again."