I had to go look that one up. He did not come right out and say that, not as you have just portrayed it.
Did you read why that was said? Not that I necessarily entirely agree with what the writer Gideon Knox said in an article entitled
I think I understand where he was coming from.
It's about what makes a person an actual Christian, rather than what makes a person a member of a certain religious tradition. Towards that idea, he does have a point. Yet another point could be that one should not assume the Copts are one and all not Christians, either. As far as I'm concerned -- if the Lord recognizes them, that's all that counts. Is that O-K with you, if I were to have than kind of opinion, and be willing to extend that in several directions at once?
I'm of the mind that where we are weak --- He (the Lord) is strong.
I may be stretching this too far (it can be stretched too far) but I also think that wherever any of us are wrong -- His righteousness, and His Grace is sufficient to overcome our own lack of perfectly understanding Him. It would all but HAVE TO be that way, or else who is that could be blessed, by Him?
Who could be drawn closer -- if they had to get everything exactly right, and 'do' 'everything right' in order for Him to accept them as His own adopted people & children? It is when we are drawn closer to Him that within ourselves we better understand Him, and can better respond to Him. Does that make any sense, to you?
From the article you linked:
Coptic believers are not Christians for the exact same reason Protestants don’t believe Catholics are Christian