One simply cannot claim to be a Christian and yet promote Romanism, its that simple.
For consideration on the various books and Colson's false gospel go here and here and here.
2Co 11:4 For if one comes and preaches another Jesus whom we have not preached, or you receive a different spirit which you have not received, or a different gospel which you have not accepted, you bear this beautifully.
Gal 1:6 I am amazed that you are so quickly deserting Him who called you by the grace of Christ, for a different gospel;
Gal 1:7 which is really not another; only there are some who are disturbing you and want to distort the gospel of Christ.
Gal 1:8 But even if we, or an angel from heaven, should preach to you a gospel contrary to what we have preached to you, he is to be accursed!
Gal 1:9 As we have said before, so I say again now, if any man is preaching to you a gospel contrary to what you received, he is to be accursed!
Gal 1:10 For am I now seeking the favor of men, or of God? Or am I striving to please men? If I were still trying to please men, I would not be a bond-servant of Christ.
There is but one way of justification which is by faith alone in Christ alone (Rom. 4), as is salvation is by grace alone through faith alone in Christ alone (Eph. 2:8-10). Rome has a false gospel of works and idolatry. This is absolutely offensive to God and damnable doctrine.