Visible evidence?

I'm doing research today on the Syro-Malabar rite church I mentioned yesterday in class, and I came across an interesting passage. The context is the author, Paul Pallath, is arguing for the historical reliability of the tradition that the church was evangelized by the apostle Thomas himself:

[T]he existence of a Christian community in South India in the name of the Apostle [Thomas] from the very first century itself, designated "St Thomas Christians", who have maintained the Christian faith for more than nineteen centuries surmounting innumerable difficulties and enduring indescribable sufferings, is an almost incontrovertible proof of the apostolate of St Thomas in South India. These Christians faithfully preserved and diligently observed throughout the centuries the "Way or Law of Thomas", only because they were fully convinced of the fact that this Way was taught to their forefathers by the Apostle Thomas himself. (Paul Pallath, The Catholic Church in India, p. 6, emphasis mine)

Now, this excerpt is taken from the end of a long list of arguments, and all the earlier arguments are more historical, and there's definitely some historical argumentation even here (i.e., the people have preserved it in each generation because they are convinced; presumably, then, the first generation was convinced St. Thomas was their apostle because they knew him). Still, there seems to be an underlying layer of "martyrdom witness" going on here: part of what's so convincing about the community's belief is how much and how faithfully they've suffered, right?

Do you find this kind of argument convincing? Clearly Pallath does. If you don't, why not, or why do you think he does?