At the very beginning of discourse I of Against the Arians the great Athanasius answers those who argued that the Arians were still Christians. I think his response is brilliant, witty, and pithy. He writes the following,
For what have they discovered in this heresy like to the religious Faith, that they vainly talk as if its supporters said no evil? This in truth is to call even Caiaphas a Christian, and to reckon the traitor Judas still among the Apostles, and to say that they asked Barrabas instead of the Saviour did no evil, and to recommend Hymenaeus and Alexander as right-hand men, as if the Apostle slandered them. (I.2)
It doesn’t get more straightforward that that. Athanasius’ answer regarding whether or not Arius and his followers are still Christians despite being heretical is sarcastically, “Yes, if Caiaphas who had Christ killed is a Christian, if Judas is still an apostle, if choosing Barrabas was not an insult to Christ, and if the Apostle Paul wrongly framed those who persecuted him, sure, then he is a Christian.” I wonder if sometimes our desire to be “fair” and “objective” prevents us from telling the truth? Sometimes I wish I was more like Athanasius.