13 But our brethren themselves, the sons of the aforesaid churches, were both ignorant at the time, and still are ignorant, of what has been done so many years ago in Africa: wherefore they at any rate cannot be defiled by the charges which have been brought, on the part of the Donatists, against the Africans, without even knowing whether they were true. But the Donatists having openly separated and divided themselves off, although they are even said to have taken part in the ordination of Primianus, yet condemned the said Primianus, ordained another bishop in opposition to Primianus, baptized outside the communion of Primianus, rebaptized after Primianus, and returned to Primianus with their disciples who had been baptized by themselves outside, and never rebaptized by any one inside.
If such a union with the party of Maximianus does not pollute the Donatists, how can the mere report concerning the Africans pollute the foreigners? If the lips meet together without offense in the kiss of peace, which reciprocally condemned each other, why is each man that is condemned by them in the churches very far removed by the intervening sea from their jurisdiction, not saluted with a kiss as a faithful Catholic, but driven forth with a blast of indignation as an impious pagan?
And if, in receiving the followers of Maximianus, they made peace in behalf of their own unity, far be it from us to find fault with them, save that they cut their own throats by their decision, that whereas, to preserve unity in their schism, they collect together again what had been parted from themselves, they yet scorn to reunite their schism itself to the true unity of the Church.
Source: Answer to Letters of Petilian, Bishop of Cirta (New Advent)