Are Catholics brothers and sisters in Christ?

I get really annoyed by sloppy comments like "You can be Catholic and be a Christian". It's a slippery, sloppy use of the idea 'to be a Catholic' and doesn't help at all.

In contrast, here are some more clear-headed and careful comments:

I would also say that many Catholics are not brothers and sisters in Christ. In fact, I would go so far as to say that a Catholic who believes what the Catholic Church teaches about justification—that it is based upon a mixture of faith and meritorious works—is likely not a brother or sister in Christ. I say 'likely' because there are some Catholics who trust fully in Christ, even though their confession of faith might state otherwise. In other words, it seems to me that the Bible teaches that one must believe with faith alone, but it doesn't require that he or she believes in faith alone as a body of doctrine. John Piper makes this point, for instance, quoting John Owen who wrote: "'Men may be really saved by that grace which doctrinally they do deny; and they may be justified by the imputation of that righteousness which in opinion they deny to be imputed.' ... Owen's words are not meant to make us cavalier about the content of the gospel, but to hold out hope that men's hearts are often better than their heads." Accordingly, some Catholics appear to fully trust in Jesus, despite the teaching of their church.

If this sounds anti-Catholic, please keep in mind that the Catholic Church says essentially the same thing about Protestants. From the Catholic point of view, the evangelical's hope in justification is found in our observance of baptism, which reflects the Catholic sacrament of baptism. We Protestants may think that we're justified by faith alone, says the Catholic, but it's actually on account of our baptism, which finds legitimacy in the sacrament of the One, Holy, Catholic, and Apostolic Church. Am I offended by the Catholic view? Well, maybe a little. But I can deal with it because I realize it's not personal, and that Catholics are simply expressing the teaching of their church with candor. Hopefully my comments are read in the same light.

(H/T Sola Panel)