After this, Celsus proceeding to speak of the Christians teaching and practising their favourite doctrines in secret, and saying that they do this to some purpose, seeing they escape the penalty of death which is imminent, he compares their dangers with those which were encountered by such men as Socrates for the sake of philosophy; and here he might have mentioned Pythagoras as well, and other philosophers. But our answer to this is, that in the case of Socrates the Athenians immediately afterwards repented; and no feeling of bitterness remained in their minds regarding him, as also happened in the history of Pythagoras.
The followers of the latter, indeed, for a considerable time established their schools in that part of Italy called Magna Græcia; but in the case of the Christians, the Roman Senate, and the princes of the time, and the soldiery, and the people, and the relatives of those who had become converts to the faith, made war upon their doctrine, and would have prevented (its progress), overcoming it by a confederacy of so powerful a nature, had it not, by the help of God, escaped the danger, and risen above it, so as (finally) to defeat the whole world in its conspiracy against it.
Source: Against Celsus (New Advent)