First, it utterly amazes me that there are evangelicals (more likely they are fundamentalists if this distinction is properly nuanced) who still think Catholics are not members of the Christian church. Some even think Roman Catholicism is a massive cult or “the synagogue of Satan.” This was not the view of the magisterial Reformers. And it most certainly was not the view of many Protestants since the 16th century; e.g. Lutherans, Anglicans, Reformed, etc.This could hardly be more out of touch with reality.
Take this example of Calvin's writings:
This is why the Church is called the mother of believers. And certainly, he who refuses to be a son of the Church desires in vain to have God as his Father. For it is only through the ministry of the Church that God begets sons for Himself and brings them up until they pass through adolescence and reach manhood. This is a title of wonderful and highest honour. But the Papists are foolish and worse than puerile when they plead this to annoy us. For their mother is an adulteress, who brings forth into death the children of the devil. How foolish is the demand that the children of God should surrender themselves to her to be cruelly slain! Could not the synagogue of Satan at that time have boasted with far more honest claim than Rome today? And yet we see how Paul strips her of every honourable distinction and assigns to her the lot of Hagar.- John Calvin, Commentary on the Epistles of Paul to the Galatians, Ephesians, Philippians, and Colossians, at Galatians 4:26
Or consider Westminster Confession of Faith 24:3:
III. It is lawful for all sorts of people to marry who are able with judgment to give their consent. Yet it is the duty of Christians to marry only in the Lord. And, therefore, such as profess the true reformed religion should not marry with infidels, Papists, or other idolaters: neither should such as are godly be unequally yoked, by marrying with such as are notoriously wicked in their life, or maintain damnable heresies.Or if you want to check in on what Luther thought, check out the Smalcald Articles (discussed here).
I'm sorry to put it this bluntly, but Mr. Armstrong is as out of touch with with history as he is, by accepting those who maintain damnable heresies, out of touch with Scripture.
But what is worse than the idiocy of supposing that the view of "fundamentalism" (as Armstrong disparagingly refers to it) today is different from that of our Reformation ancestors, is Mr. Armstrong's foolish notion that leaving Roman Catholics in Roman Catholicism is "love." It's exactly the opposite of love!
Love is sharing the good news with people. Love is warning people about their condition. Love is not letting an ill man think he is well, but rather love is persuading the sick man of his need for the Physician.
There's probably more that could be said to correct the many errors in Mr. Armstrong's article (for example, he writes that "Calvin and Luther make interesting reading here since they struggled against Rome yet still held some doctrinal beliefs that modern evangelicals remain uncomfortable with (views about Mary, etc.)," (see his article) yet Calvin did not hold "doctrinal believes" about Mary that modern evangelicals would "remain uncomfortable with" - see my discussion here). Nevertheless, the biggest error and most horrible error is Mr. Armstrong's encouragement to those in Rome to stay in Rome under the guise that this is more loving than evangelizing them.