I resent being accused of not being a “true” Christian.
This is a harsh and unnecessarily divisive posting.
As a former Protestant now Catholic, I'm inclined to agree. One can make their case for the papacy without stating that other followers of Christ who disagree aren't "true" or real Christians. I didn't bother reading the article because Catholicism doesn't teach that our separated brethren aren't "true Christians." Any Catholic tempted to doubt this can refer to paragraphs 817-819 of the catechism.
From 818: [O]ne cannot charge with the sin of the separation those who at present are born into these communities [that resulted from such separation] and in them are brought up in the faith of Christ, and the Catholic Church accepts them with respect and affection as brothers....All who have been justified by faith in Baptism are incorporated into Christ; they therefore have a right to be called Christians, and with good reason are accepted as brothers in the Lord by the children of the Catholic Church.
Peace be with you.